The history of the anti-heroic angel Castiel from Supernatural.
Arrival on Earth
Although not much is known about Castiel's early life, discussions with Uriel suggest the pair were children by Angel standards when Lucifer had rebelled against Heaven after he refused to bow down to humanity. While his brother was enthralled by Lucifer's power and charisma, Castiel remembered being frightened and disturbed by the rebellious Archangel. Castiel had been stationed on Earth for at least 2,000 years while being in the same garrison as Anna, who had acted as his superior and they were very close. Castiel also became very close to his brothers and sisters: Uriel, Balthazar, Hester, Inias and Bartholomew. Castiel was present when the world was first created, making him several thousands years old biblically (Uriel also referenced their long servitude, being "6 or 7 centuries"). Castiel watched as the first fish emerged from the ocean being told by an older brother not to step on it as the fish had a long destiny. He also watched the humans build the Tower of Babel, among other historic and Biblical events. He also witnessed the evolutionary struggle between Homosapiens and Neanderthals and was hoping that the latter would survive because of their superior poetry (though this particular opinion and reasoning may have just been madness). He also witnessed Cain killing Abel.
At the end of the third season of Supernatural, main character Dean Winchester is in Hell after being killed by the hellhounds of the demonic antagonist Lilith.
In the season four premiere "Lazarus Rising", under the orders of Heaven, the angel Castiel is introduced as the one who brought Dean back from Hell and resurrected him. Because merely perceiving his actual form typically results in blindness, he takes on a human host—James "Jimmy" Novak, a "devout man" who prayed for it—to communicate with Dean, and tells him that he has been brought back because God has work for him. Lilith is breaking the 66 seals in order to free Lucifer, and that Dean must stop her.
In 2008, Castiel spoke with his true vessel, Jimmy Novak, in Pontiac, Illinois. When Jimmy is watching television, Castiel's voice distorts the picture and causes Jimmy to scream in pain and his body to spasm until he finally blacks out. Later, Castiel was able to make true contact with him and tells Jimmy to put his arm in boiling water and that he would be unharmed as a way to prove his faith. With his wife believing that he was going crazy, Jimmy asks Castiel what he wants from him and how he can help. Castiel explains that he needs to use Jimmy as a vessel, to which Jimmy agrees to as long as his family is protected. Castiel promised he would look out for the Novak Family.
After receiving consent, Castiel possesses Jimmy's body. Before he leaves, Castiel is confronted by Jimmy's daughter, Claire, and calmly tells her that he is not her father.
When Dean Winchester broke the first of the 66 Seals by torturing souls in Hell that would allow Lucifer to walk free again, the Angels took action. They fought their way into Hell and Castiel personally freed Dean from the pit, resurrecting him. Dean awoke in a grave and made his way to the surface, not knowing how he had returned to life; the only clues he had was the damage of the area his grave was at, his healed body from the hellhound attack and a large burn imprint of a hand near his shoulder. Dean also heard a shriek (which was Castiel's true voice) but he was struck by pain at the sound as it shattered the windows.
After reuniting with Bobby Singer and Sam Winchester, Dean tried to learn who and what had rescued him from Hell as well as why. He also discovered that he'd been dead and buried for four months. Eventually, Dean met a psychic named Pamela Barnes and learned through a séance the being who saved him is named Castiel who had warned her to turn away but she didn't listen and her eyes were burned out after seeing his true form.
Dean soon took matters into his own hands and with Bobby's help, set a trap for the creature and protected himself and Bobby with multiple Devil's Traps and other anti-demon devices laid out. Castiel arrived as the hunters shot at him as he passed through the Devil's Traps with ease. Dean questioned his identity as Castiel revealed to Dean that he is the one who rescued him, as the latter sarcastically thanked him and stabbed him with Ruby's knife but it had no effect and Castiel counter an attack from Bobby and quickly knocked out him with a mere touch as Castiel explained that he and Dean needed to talk alone. He told Dean Bobby was alive and told Dean what he was by stating "I'm an angel of the Lord." At first, Dean didn't believe him as Castiel criticized his lack of faith before he revealed his wings to prove his claims. Though greatly shocked to see an actual angel, Dean berated him for burning out Pamela's eyes as Castiel mentioned that he did warn her to turn back as his true form was overwhelming. Castiel soon tells Dean it was his true voice that had been the shriek Dean heard, as special people can understand but Dean wasn't one of them so Castiel had to possess a devout man to better communicate. Dean then asks why he was resurrected and Castiel tells him that God commanded it as he has work for him.
After people who were supposed to be dead seemed to be rising from the grave, Castiel appeared to Dean and explained to him that this was one of the 66 Seals, "The Rising of the Witnesses." Castiel told him that Lilith was attempting to break 66 of the seals which would lead to Lucifer walking free on Earth and then the Apocalypse would begin. The Angels had been fighting to stop the demons, but the odds were against them. He explained to Dean that he must help stop the breaking of the seals as well. Castiel also showed that he was not a force to be underestimated or even taken lightly as in a chilling tone, he told Dean to start showing him some respect or he'd change his mind and throw him back into Hell again.
One day when Dean was asleep, he woke up to find Castiel sitting beside him. Castiel, without speaking, tapped Dean and brought him back in time to an important few-day period. It showed Dean the connection between Azazel and Mary Winchester, and answered questions that had always been on his mind. Castiel said that the reason he had brought Dean back to that period was to make sure that he was caught up with all of the facts. He also explained that the angels are still unaware of Azazel's endgame. Castiel also told Dean about Sam's developing abilities and that he was going too far down a dark path and that if Sam did not stop using his powers, then the angels would kill him. Through this Dean learned of Sam's continued use of his psychic powers.
Sometime later, Castiel and his partner Uriel met with the Winchesters when they were in the middle of hunting a witch. It was here that he met Sam Winchester for the first time and was cautious, due to the latter having demon blood in his veins but was happy to hear he stopped his activities. The angels explained that the witch was trying to summon the demon Samhain from Hell and that this was another one of the 66 Seals. The angels said that they would have to destroy the entire town and all of its residents to ensure that the seal would not be broken. The brothers argued against this and assured Castiel and Uriel that they could stop the witch from summoning Samhain. While Uriel wanted to smite the town anyway and drag Dean and Sam away, Castiel agreed with them, later discussing with Uriel his disdain for humanity and their true orders. Unfortunately, the Winchesters failed and Samhain rose, breaking another seal. After Sam exorcised Samhain with his powers and stopped him, Castiel met with Dean in a park and revealed that the angels true orders were always to follow Dean's orders, not to smite the town and that this was a test of Dean's battlefield leadership. Castiel reveals that he always hoped that Dean would chose to save the town whether or not they failed and that he secretly harbors doubts about Heaven and its plans.
When the angels learned that a woman named Anna Milton could listen in on angel's conversations, they grew worried as they thought of the possibility if demons were able to get to her before them, the demons would know everything that the angels were planning. But Castiel knew the truth: Anna had once been his angel superior Anna who disobeyed. She cut out her Grace and fell to Earth, where she was reborn as a human. Castiel and Uriel knew though that the only way to ensure the safety of their plans were to kill Anna. While Castiel was hesitant about this, Uriel enforced the idea that it was absolutely necessary.
Castiel and Uriel found Anna along with the Winchesters. The angels ordered Sam and Dean to hand over Anna, but they refused. The angels attacked them and almost retrieved Anna, but were sent away by a ritual Anna performed. After Uriel threatened Dean that he would kill Sam, the latter gave up his and his brother's location. They later were able to find Anna with the Winchesters again, but soon discovered that they had been led into a trap when Alastair arrived with a group of demons. The angels and demons fought over who would take Anna with Castiel fighting Alastair. Castiel proved no match for the demon, with his powers being useless, but Dean saved him despite being on opposite sides of the Anna situation. In the end, Anna retrieved her Grace and became an angel again and Alastair's body was destroyed, defeating him. Grateful for Dean saving him, Castiel held Uriel back from attacking Dean in revenge and they left to chase after Anna.
When Alastair tried to break another seal by killing two Reapers on the night of the Solstice, Castiel managed to capture him having pretended to be Bobby to send the Winchesters after the seal. The angels held Alastair captive and when seven angels had mysteriously been killed, Castiel assumed that demons were behind the attacks. He and Uriel recruited Dean to interrogate the demon. During the interrogation, Anna returned and spoke with Castiel. She told him that she knew how he was feeling and that he was beginning to develop human emotions. Castiel refused to believe this and yelled at his sister, causing her to leave. Shortly after, the Devil's Trap, Castiel had made to hold Alastair somehow malfunctioned and Alastair nearly killed Dean. Castiel intervened and fought the demon but was almost sent back to Heaven when Sam came to his rescue, using his psychic powers to kill Alastair to Castiel's shock after torturing out of him that the demons weren't responsible for the angel deaths. While visiting Dean at the hospital, Sam criticized Castiel for being so cold-hearted as to risking Dean's life. This sunk into Castiel's head and he went to Anna for help, telling her he needed to know what to do; she told him it was time for him to decide on his own for once. Castiel investigated the broken Devil's Trap further and learned that it was Uriel who was behind the malfunctioning Devil's Trap and the angel killings.
Uriel reminded Castiel of the times when Lucifer was one of the greatest angels and also spoke about how God isn't doing anything and they must follow someone who would. Castiel refused and the two angels fought. Castiel put up a good fight but was overpowered by Uriel and nearly killed but was saved when Anna appeared and killed Uriel with his own Angel Blade. Castiel then went to Dean and confirmed that Dean was responsible for breaking the first seal by giving in to Alastair's torture. Dean begged Castiel to find someone else because he wasn't fit to stop the Apocalypse.
Castiel later appeared when Dean interrogated a writer named Chuck Shurley (who unknown to him was really God) writing a book series based on the Winchester brothers, explaining that Chuck was a Prophet of the Lord. When Dean asked him for help in saving Sam from Lilith, Castiel was initially hesitant to help, which caused Dean to berate and refuse help. Castiel stopped Dean by dropping him a hint by telling him that Prophets are protected by archangels, and that if a Prophet is in the same room with a demon, then the archangel will descend to smite the demon. This gave Dean the idea to put Chuck in the same room with Lilith to save Sam and he thanks Cass for the help.
Castiel then came to Dean while he was dreaming and told him to meet him at a certain location, saying that he had something to tell them. But when Dean and Sam arrived, they found him unconscious in a wrecked building with dead demons. When he awoke, the brothers found that Castiel had abandoned his vessel, Jimmy Novak, who describes being possessed by Castiel like "being chained to a comet." When Dean, Sam, Jimmy and Jimmy's daughter, Claire, were being held hostage by demons, Jimmy was shot and Castiel returned to possess Claire and helped save them all. While Castiel tried to comfort a dying Jimmy, Jimmy pleaded with Castiel to take him back as a host and Castiel accepted. When Dean asked Castiel what happened, he coldly replied, "I learned my lesson while I was away, Dean. I serve Heaven; I don't serve Man. And I certainly don't serve you."
Later in When the Levee Breaks Castiel was summoned by Dean, who was screaming for three hours for help. When Castiel arrived, Dean asked him what happened in Heaven, but Castiel wouldn't say. Then Castiel recruited Dean in the service of God and his Angels. Castiel told him to wait till the Angels summons him. A few hours later he freed Sam from Bobby's panic room in which he was held captive, because of his addiction. Later Anna confronted Castiel about why he released Sam. Anna said that Sam was even worse than they had expected. Castiel told he has his orders to follow and then said to Anna that she shouldn't have come. The next moment two Angels stood beside her, and took her captive.
Later Zachariah brought Dean to a chamber, so he would be safe for the release of Lucifer. Zachariah told him that the final seal would be broken that night. Although had a fight with Sam, Dean tried to contact him on his cellphone, leaving a message on his voicemail. Later Dean wanted to talk with Sam and summoned Castiel by breaking a Stone Angel on one of the tables. Dean asked to visited Sam, but Castiel said he could go everywhere except to Sam. Dean asked what they were going to do with Sam. Castiel said that Sam is going to do it to himself, but he didn't want to say more. He said it was his destiny. Dean said that destiny was just a bunch of lies, to keep him in line. Dean tried to persuade Castiel to help him, but Castiel said that they would be all be hunted, that they would all be killed. In response, Dean said to him that this is worth dying for. But to Dean's disappointment, Castiel refused and Dean ordered him away. Castiel tried to get Dean to listen, but left when he refused.
Shortly after, Castiel confronted Dean and took the demon killing blade as he drew an Angel Banishing Sigil on the wall with his own blood after putting his hand over Dean's mouth to stop him from shouting until he realized Castiel was helping him. Zachariah then appeared and asked Castiel what he was doing. Castiel responded by pressing his bloody hand on the sigil, banishing Zachariah. He then told Dean that Lilith is the final seal and that Sam is going to break it by killing hr. He said he knew someone that knew where Sam was and teleported Dean with him.
Castiel teleported Dean and himself to Chuck, the prophet of the Lord (who unknown to Castiel was God). Chuck was confused at their arrival, as he said that this is not supposed to be, that they were not in the story. Castiel said that they would make it up. When they found out that Sam was at Saint Mary's, Chuck’s computer goes off and bright light fills the room. Castiel said it is the Archangel and teleported Dean to Saint Mary's, so that he could hold the Angel off.
At Chuck’s house, Castiel looks up at the bright light and prepared to face Raphael. Seeing his expression, Chuck puts his hand on Cass’ shoulder to reassure him, but when Castiel gives him a look, he removes it.
After witnessing the release of Lucifer from Hell, Dean and Sam went to Chuck's house to find Castiel. There they were told by Chuck that the Archangel smoked Castiel - literally - and they even find one of his teeth tangled in Chuck's hair. When Zachariah appears, Dean banishes him while stating he learned the trick from his friend Castiel.
Later, when the Winchesters are trying to track down Michael's sword in their father's old storage unit, Zachariah and his angels arrived to inform Dean that he is Michael's sword—in other words, Michael's vessel. When Dean refused to give his consent for Michael to possess his body, Zachariah started inflicting various kinds of physical pain on him and Sam (breaking Sam's legs and removing his lungs, and giving Dean stage-four stomach cancer), all the while refusing to kill them for more torture. Castiel then miraculously appeared on the scene and dispatched Zachariah's men, as a shocked Zachariah questioned his return. Castiel hinted that God was responsible for his resurrection as he was with saving Sam and Dean, this caused Zachariah to become scared as he originally believed God left. Castiel then forced his brother to heal the Winchesters and leave the area, with the latter reluctantly complying with his demands. Castiel then used his powers to carve Enochian Sigils on their ribs, keeping them hidden from all demons and angels, including Lucifer and himself.
After rebelling against the angels, Castiel's powers began to slowly deteriorate whilst he searched for God using Dean's amulet. However, despite his vanishing strength, he continued to be invaluable help to the brothers saving them on numerous occasions.
Looking for a way to find God, Castiel approached Dean to help him capture Raphael to interrogate him about God's location. After Castiel retrieved Holy Oil for the trap, Dean took him to a strip club after learning that Castiel was a virgin so he wouldn't die as one. Castiel was clearly nervous in the strip club and ended up angering the stripper by telling her that her father left because he hated his job, not her. Castiel and Dean succeeded in trapping Raphael who told them God was dead. Though Raphael demanded his release and threatened them, Castiel left him where he was telling him that "for now you're my little bitch."
Castiel later contacted Dean about finding The Colt and waited on Dean who needed rest. That night, Zachariah sent Dean to an alternate post-Apocalyptic future in which Lucifer had ravaged the world with the Croatoan Virus, the Angels have abandoned Earth and Castiel loses his remaining powers (though he is still able to sense that the Present Dean is from the past) and was human. He joined the Future Dean's resistance movement against Lucifer, but quickly became bitter and depressed with the situation. As a result, he spent most of his time immersed in drugs and women. Future Castiel participated in the failed attack on Lucifer at the end of the episode. He was presumably killed along with the rest of the Future Dean's group. After Dean returned from the era, Castiel rescued him from Zachariah stating he and Dean set an appointment. After seeing a future where Castiel was human and perpetually stoned, Dean told him never to change.
When Sam and Dean were kidnapped by the Trickster, Castiel came to their rescue, but was stopped as the trickster banished him. He later made his way back long enough to warn them that the Trickster was too powerful to be a Trickster before he was knocked him away. The Trickster himself appeared and bound Castiel's mouth as he greeted him amicably before effortlessly banishing him. Castiel's information and the Trickster's familiarity with him was one of the various clues that caused Sam and Dean to realize the Trickster was actually an angel. After trapping him in a circle of holy fire, they force him to reveal his identity which is the Archangel Gabriel. They soon forced him to bring Castiel back from wherever he put him. Returning roughed up, Castiel greeted his older brother coldly (revealing he figured out his identity as well) as the latter taunted him of his pointless search for their father. Castiel soon watched the end of Sam and Dean's confrontation with Gabriel, which ended with Dean freeing him from the fire.
When Sam, Dean, Ellen and Jo went after Lucifer, Castiel joined them, drinking shots with Ellen before they took off and taking a picture with the group. In Carthage, Castiel separated from the group to follow a Reaper and was captured and held in Holy Fire by Lucifer who tried to convince the angel to join him. Castiel refused and was held captive by Meg who taunted him. However, Castiel managed to loosen a pipe and use it to knock Meg into the circle where he tried to smite her only to find he'd lost that power. Castiel used Meg's body as a bridge to escape and teleported Sam and Dean, the only other survivors of the failed mission away from Lucifer.
When the brothers were ambushed and killed by several hunters furious with them for causing the Apocalypse, Castiel warned the brothers that Zachariah was looking for them in Heaven and they should attempt to contact an angel named Joshua, Heaven's Gardner who was rumored to speak to God. During the Winchesters talk with him, it is confirmed by Joshua that God is the one who resurrected Castiel. When the brothers returned from death, Sam revealed that God wanted nothing to do with them, causing Castiel to abandon his belief in God and return Dean's amulet, stating that it was worthless. He fell into a depression and drank heavily, but sobered up in time to help defeat the Whore of Babylon.
In Point of No Return, Castiel was angry with Dean's decision to say yes to Michael as he had sacrificed everything to follow Dean as he believed in him. Castiel soon brought the Winchesters' their half-brother Adam Milligan who was resurrected to replace Dean as Michael's vessel. Dealing with these two problems, the group put Dean in the panic room and kept Adam under watch after hiding his presence from the angels.
At one point, Dean banished Castiel but the latter returned and proceed to beat him up out of pure rage. When Sam and Dean go to rescue Adam from Zachariah, Castiel carved an Angel Banishing Sigil into his chest and uses it to banish four angels and himself after showing his lack of faith in Dean by saying at least he won't have to see Dean fail. However, Dean ultimately doesn't go through with saying yes to Michael and kills Zachariah instead.
In Two Minutes to Midnight, Castiel returned powerless, apparently from the banishing sigil. He apologizes to Dean for doubting him and comes to their aid when confronting Pestilence. In his weakened state, Pestilence easily brings Castiel down, but he possesses just a "speck" of his angelic self left, just enough to resist Pestilence's power long enough to cut off his ring and defeat him. Castiel later joins Bobby and Sam in an assault on Niveus to stop the Croatoan Virus, bemoaning his lack of power. Despite this, Castiel does a good job, stopping a truck loaded with the virus from leaving and killing a zombie with a shotgun (which he remarks is actually useful), saving Sam's life.
In Swan Song, now almost completely human, Castiel accompanies Bobby, Dean and Sam to Detroit where Sam will say Yes to Lucifer as part of their plan. Castiel awkwardly says goodbye to Sam and tries to reassure him that they will be okay, but is bad at it. When Sam fails to overpower Lucifer, Castiel loses hope and suggests they get drunk and wait for the end to come. Dean refuses to give up and manages to get Castiel and Bobby to help him. In the final confrontation, when Michael (in the vessel of Adam Milligan) was about to fight Lucifer (in the vessel of Sam) Dean intervened saying he wished to speak with Sam. This prompted Michael to remove Dean, however, before he could respond Castiel teleported into the field with Bobby and threw a Molotov of holy fire at Michael sending him back to Heaven for a brief time. Lucifer turned to Castiel, furious by the fact that Castiel harmed his brother, and caused Castiel to explode. Shortly after the battle between Dean and Lucifer where Sam was able to retake control and throw both himself and Michael into the Pit, Castiel was resurrected by God with his angelic powers restored and upgraded, allowing him to restore Dean's broken bones and Bobby to life. Castiel, now a Seraphim, said that he needed to return to Heaven to restore order to the anarchy that will follow Michael's departure.
Sometime later, Castiel used his new power to raise Sam out of the cage but accidentally left the latter's soul behind.
After the Apocalypse was averted, Castiel returned to Heaven where other angels awaited him. He tried to tell them about freedom, but none of them understood. Castiel finds out that the archangel Raphael wanted to take over and follow Michael's departure and restart the Apocalypse. Unable to stop him, Castiel wants to turn to Dean, but doesn't because he feels like he's already asked so much from Dean. Then Crowley shows up with a deal to find Purgatory and offers Castiel power to stop Raphael. So Castiel begins a civil war in Heaven. When Sam and Dean found out the plagues were unleashed upon the Earth, they called Castiel for help. Castiel showed up and told them the Angelic Weapons were stolen from Heaven. He also claimed that he didn't know what or whom brought Sam back from Hell.
During their investigation, they find out that an Angel has been moonlighting as a crossroads demon. To locate the angel's name, Castiel performed a ritual to find the angel that bought the soul. When Castiel learned it was his brother, Balthazar, he was shocked to see him as he thought him dead before an angel follower of Raphael showed up and attacked Castiel. Castiel managed to defend himself and let the angel get away, but the angel knew that Balthazar was selling pieces of the Staff of Moses. So Castiel, Dean and Sam try to find Balthazar first, and when they do, Balthazar admitted that he stole the weapons from Heaven and that he want to live in freedom. When Balthazar disappears, Castiel is confronted by angels who want to kill him. Castiel asked them to join him, but they refused and Castiel killed them. Afterwards, Raphael showed up and told him that they were his followers and smashed Castiel. Just as Raphael was about to kill Castiel, Balthazar showed up and used the weapons from Heaven to destroy Raphael's vessel. Eventually, Sam and Dean showed up and were able to trap Balthazar in a circle of holy oil, but Castiel lets Balthazar go after they force him to let go of his hold on the soul with Castiel's reason being that he owed Balthazar his life.
Dean becomes more and more disturbed by Sam's behavior, and prays for Castiel's help. Castiel doesn't respond until Dean calls him about a possible loose nuke, much to Dean's aggravation. Castiel apologizes, but reassures Dean on his theory that Sam is not Lucifer, explaining that all angels would feel his presence if Lucifer was free. Castiel also states he doesn't know what's wrong with Sam, but he promises to make inquiries. Dean calls on Castiel once he has Sam unconscious, and asks for him to diagnose Sam. Castiel informs both brothers that physically, Sam is perfectly healthy, but his soul is missing. He guesses that Sam's soul is still in the cage with Michael and Lucifer. When Sam goes with Samuel as his only lead, Castiel follows Sam and Dean to the Campbell Compound to check if Samuel has a soul or not, which he does. However, before he can do any more to help, he states he needs to return to Heaven, but reassures Sam and Dean that their problems "always come first", and will keep in touch.
Castiel is later called on for assistance by Sam, who tricks him into leaving Heaven by saying he and Dean have found the Ark of the Covenant. Sam tries to coerce Castiel into joining them along with the demon Meg and her minions to confront Crowley, but fails as Castiel knows Sam can't harm him. However, recognizing that Sam really does need help, Castiel decides to help anyway. Castiel tries to track down Crowley by means of a ritual, which leads them nowhere. When the group is caught by Samuel as they search through his quarters, Dean asks for the angel to leave back to their motel.
Sometime later, while Sam and Dean are looking through records trying to find Crowley, Castiel is confounded by watching porn, which he states just happened to be on the TV. He creates an awkward moment, even weirding Samuel out upon arriving at their motel. He leaves with the group after Samuel gives them the location of Crowley's prison. Before leaving for the prison, Castiel suggests to Dean that he doesn't think restoring Sam's soul is wise. He supports his statement with the fact that his soul has been locked in the cage with Michael and Lucifer for more than a year, and they have been doing nothing other than taking their frustrations out on Sam. He theorizes that if they try to force the damaged, tortured soul back into Sam, and if they fail to deal with the problems, then Sam will suffer horrifically.
The group then leaves for the prison, and Castiel finds a back entrance inside. Shortly after, hell-hounds come after the party. Meg distracts Castiel by kissing him, and steals his angelic blade. Castiel, surprisingly, responds to this by kissing her back, stating he learned that from the porn he was watching earlier. The boys then run off while Meg holds off the hell-hounds with the angel blade. Later, Castiel is banished by a blood sigil cast by Samuel, while the Winchesters are taken captive.
While Crowley has the boys pinned to the wall, Castiel reappears, carrying a large bag. After Crowley taunts him about his losing war against Raphael, Castiel reveals that the bag contains his salvaged bones. The angel asks the King of Hell one last time if he can restore Sam's soul or not. Crowley says he cannot, and Castiel proceeds to burn his bones, turning him to ash.
A short moment later, outside the prison, Castiel later admits that he is on the losing side of the civil war in Heaven, and expresses disappointment as he wishes much of the time that circumstances were different as he prefers being on Earth with Sam and Dean. Dean then reassures the angel that they will help in whatever way they can, and that the brothers are his friends. Castiel then turns to Sam, and reassures him that they will find another way to get his soul back. Sam then asks him to dispose of the monsters that still remain inside the prison, to which Castiel presumably leaves to do so.
After Sam gets his soul back, Castiel comes to check up on him, and tells Dean that he doesn't think Sam is ever going to wake up. A few hours later Sam wakes up and reunites with his brother. Later on Sam, now with his soul, calls Cas. Castiel comes and tells Sam he is glad to see him well, despite everything, nearly hugging him. Sam catches on and tricks Castiel into telling him the truth.
In My Heart Will Go On, Castiel saves Sam and Dean from Fate, when she tries to get her revenge for stopping the apocalypse. He tells the brothers if they want to live, they need to kill Fate. So Sam and Dean draw Fate out and just as they face their death, time freezes. Castiel confronts Fate and she reveals the real reason why Balthazar saved the Titanic. It was because Castiel ordered Balthazar to do it for the souls. She threatens to kill Sam and Dean unless Castiel fixes history. Castiel orders the creeping Balthazar to stop and right history.
In Frontierland, Cas returns to send Sam and Dean back to the Wild West so the brothers could acquire ashes of thephoenix, the one thing that could kill the mother of all. He tells Sam and Dean they have only 24 hours, after that he will no longer be able to find them. During the time the boys are in the Wild West, Castiel's lieutenant, Rachel, confronts him about his side dealings Castiel is doing to win the war. This leads to a duel between the two, and Castiel emerges the winner and wounded. He soon heads to Bobby's, draws a symbol in his blood and passes out. As time grows short, Castiel re-awakens, but is very weak and low on power. In order to "power up" he tells Bobby he needs to touch Bobby's soul. Once powered up, Castiel brings the boys back.
Now with the ashes, the hunt for Eve is on. Castiel comes to Sam and Dean asking for Eve's location, but they too are unsuccessful. Sam suggests that they find a monster who would be willing to give them Eve's location. Castiel finds and brings Lenore, who gives them Eve's location, in exchange for her death. Sam is hesitant, but Castiel brings Lenore her end. This action makes Sam and Dean concerned about Castiel and his circumstances. Once they arrive in Oregon, Castiel discovers he can't use his powers, and is now powerless, thanks to Eve. Castiel is able to torture Eve's location out of a Jefferson Starship, but is captured by her monsters. After Dean kills Eve, Castiel's powers return and he slays the Jefferson Starships with a blast of white light. Castiel is later revealed to be working with Crowley after the Winchesters' encounter with Eve.
The truth finally comes out in The Man Who Would Be King, Castiel recounts history from his point of view and how the Winchesters inspired him. Castiel also begins to notice that Sam, Dean and Bobby are getting suspicious of Castiel and believe he is working with Crowley. Castiel recounts about his return to heaven and his favorite place (the heaven of a 40 year old man who drowned in a bath tub). This is after him revealing he brought back Sam from hell, sans his soul.
At the time, Castiel did not know Sam didn't have his soul. He also tries to get other angels to embrace freedom, but the angels don't know how. Then Raphael tries to make Castiel bow to him, and Castiel refuses. Due to his misfortune, Castiel is no match for him. Castiel tries to get help from Dean, but seeing Dean retired makes Castiel rethink this. Then Crowley approaches Castiel with a deal, so Castiel can become more powerful. Castiel begins his deal with Crowley. With this deal, Castiel starts the civil war in heaven. But when Crowley begins to threaten the Winchester's lives, Castiel becomes protective of them.
Although Castiel managed to keep the secret for a while, he slipped up with information he got from spying on them. Later the boys and Bobby trapped him in a ring of holy fire, where they confront him about his betrayal. Castiel tried to maintain his loyalty to them even revealing he was really the one that brought Sam back from the cage but this brings further problems as he is accused of bringing him soulless on purpose.
When demons come, Castiel tells the boys to run and they leave him in the ring of holy fire. Crowley comes in and saves him. Castiel leaves, and comes to Dean, trying to explain the situation. Castiel tells Dean that he did this for Dean but Dean does not want it this way. Castiel responds that Dean can't stop him and says he's sorry and disappears.
In Let It Bleed, Castiel has taken one of the Campbell diaries, and is investigating an incident in which H.P. Lovecraft opened a portal to another world. Sam prays for him, telling Cas that Lisa and Ben have been kidnapped by Crowley, and asks for help. Castiel listens unseen, and does not answer, but goes to confront Crowley. He insists that the demon not harm Lisa and Ben, but Crowley refuses to make such a promise. Balthazar later calls him. He asks Cas if he is planning on opening the door to Purgatory; Cas lies that he is not, but Balthazar is not fooled. Castiel asks if he is with him, or not. Balthazar says he is.Castiel goes to Dean, arriving just in time to save him from a demon. He apologizes for Lisa and Ben, revealing that he did not know Crowley's plan. Dean is skeptical, and angry. Castiel asks him again to support his decision to tap the souls in Purgatory. He pleads with him that he has always done what the brothers needed him to, asking little in return. Cas asks them to trust in him, and promises to bring him his family afterward. Dean is unwilling, and Castiel leaves. After Dean and Sam rescue Lisa, Castiel comes to the hospital where the gravely injured Lisa is not expected to survive. He apologizes again, but Dean is not forgiving. Castiel says that he did not come for Dean, then places a hand on Lisa's forehead, healing her. Both Dean and Cas acknowledge that this does not change their situation, but Dean asks for an additional favor. Castiel removes all Lisa and Ben's memories of Dean. Later Castiel finds and takes Dr. Visyak, the creature he needs to open Purgatory.
In The Man Who Knew Too Much, Castiel and Crowley torture Dr. Visyak until they obtain what they need to open Purgatory. She escapes and contacts Bobby and the Winchesters, telling her story before dying in an alley from her injuries. Castiel comes to the three hunters, who are outraged. Dean tries to argue with him again, but Cas cuts him off, saying he no longer cares about Dean's opinion. He then touches Sam's head, breaking the mental wall, and promising to repair him as long as Dean stops the opposition.
Castiel meets with Crowley, who has assembled the necessary ingredients. The angel wants to renegotiate their deal. He will not give Crowley the souls, so Crowley can either flee or die. The demon leaves Castiel with the blood for the ritual. Later, Castiel confronts Balthazar. He says that Dean is coming, and someone among them is a traitor. Balthazar asks him who it is, and Castiel lies that he does not know, and wants Balthazar to investigate. While the other angel is distracted, Castiel stabs and kills him. Just before the ritual is meant to begin, a cloud of demons descends around the building, and Crowley appears. Castiel tries to kill him, but cannot. He has a new partner in Raphael. Castiel is surprised at the partnership with their differing goals, but both seem to think they have taken the best course available. They demand the blood; Castiel throws them a jar and leaves. Crowley conducts the ritual, and though Bobby and Dean try to interrupt, completes it.
Nothing happens and Castiel reappears. Crowley realizes that he switched the blood, and conducted his own ritual. Castiel displays his power briefly in a flash of energy. Crowley, realizing the game is up for the time being, wisely disappears, and Raphael asks for mercy.
But Castiel is not in a forgiving mood. He snaps his fingers, obliterating Raphael to pieces in mere seconds. He turns to Dean and Bobby. He was right, he says, and he did save them. Dean nervously agrees, then suggests that Castiel should return the souls, and disarm himself. Castiel says he has Raphael's followers to deal with. Dean is worried, and reminds Castiel that he is family, and he doesn't want to lose him. Castiel says that he has no family anymore; he will not give up the souls.
Using that moment, Sam stabs him from behind with an angel sword, but nothing happens. Castiel greets him, then says the sword will not work because he is not an angel anymore. He says that he is their new God, and that they must venerate him, or be destroyed. As he says those words, Dean, Sam and Bobby look on in horror, realizing with shock that their former ally and friend has become a power-hungry angel who believes that he is God.
Castiel waits for Sam, Dean, and Bobby to show their respects. Bobby goes to his knees, and motions for Sam and Dean to do the same. Dean and Sam begin to kneel, but Castiel stops him, and orders Bobby to stand, saying that there is no point if they do not mean what they do. Castiel observes, without turning to look, that Sam is not doing well. Dean reminds Cas that the former angel promised to fix Sam when it was over. Castiel cuts him off; his promise was contingent on Dean not opposing him further, and oppose him Dean did. Castiel tells them he has no need to kill them, though he no longer has any regard for them, and will let them live if they do not plot against him.
Castiel sets out to right the wrongs he sees. He destroys Raphael's followers in Heaven, vaporizing thousands of angels, and tells the survivors that he no longer thinks free will is what Heaven needs. Instead, he will give them a firm hand. He appears in a church, reveals his identity, and smites a hypocritical preacher. He leaves an image of himself in the stained glass as he departs, and accidentally burns a pew as welts appear on his hand.
He finds Crowley hiding in a RV, and tells him that he may retain his position as King of Hell, but that Castiel will choose which souls he receives. He claims that he would have destroyed Hell completely, but he needed it to threaten his enemies, and maintain Michael and Lucifer. It is unknown if he actually had the power to destroy Hell, or he was over his head will all the souls inside him. He leaves after looking at yet more open places on his skin. He gives money to a blind man on the street, and heals the man for his faith. The man is grateful, but surprised when his first sight is of Castiel's blistering face. At a nearby bathroom, he looks in the mirror and stares at the blisters covering his face and hands. His stomach begins to bulge and contort as the Leviathans demand to be let out, whispering to him as he looks down in horror, mumbling "No."
Sam, Dean, and Bobby summon Crowley, who reluctantly gives them a spell to bind Death. They work it, and an irritated Death appears, followed shortly by Castiel. Dean orders Death to kill 'god'. Death says he sees only a mutated angel, one whose vessel is disintegrating. Castiel, sounding uncertain, says he will heal himself when his works are complete. Death replies that Castiel swallowed Leviathans when he emptied Purgatory, not just souls, and that is the danger. Castiel frees Death from Dean's binding spell.
Castiel leaves. At a political election office campaigning for a senator of whom Castiel disapproves, he is stopped by one of her aides. Castiel asks the man to see that he is a good god, that he means the best for his children. He awakes some time later in a pool of blood on the floor. He has slaughtered the entire office. At Bobby's place, Sam prays for Castiel to reconsider and give up the souls. A few minutes later Castiel appears, disheveled, bloody, and looking ill. He says he needs their help.
He listens to Sam's call and agrees to put all the souls back in Purgatory. Before the opening of the door, he expresses regret at what he has done and wishes that he could have restored Sam back to normal, and promised to do so if he survived. After he lets out all the souls, Cass passes out but wakes up. He automatically begins to contort and struggle as the Leviathans had held on to his body are trying to take over.
Castiel is soon overpowered by the Leviathans who in turn take control of him, presumably taking him far away. They begin by throwing Dean and Bobby against a wall before saying that they're going to have fun now. Soon after flinging them, his vessel begins to ooze black blood, and Dean smugly points out that the vessel can't contain the power of the Leviathans. They leave saying they will be back for Dean. The Leviathans are able to guide Castiel's vessel to a water reserve and the vessel explodes in a whirlpool leaving the Leviathans to escape into the water. Later, his trenchcoat is found, Dean folds it up and takes it with him.
It was later revealed in Slash Fiction that the Leviathans learned of Sam and Dean's aliases from Castiel's mind before they sent him away.
Castiel returns in The Born-Again Identity, having been resurrected by God yet again, but has forgotten his previous life as an angel. He now lives as Emmanuel, a healer with his wife. Dean finds him again after word of his healings get out. Dean saves his wife and asks him to heal Sam. After regaining his memories as he is smiting multiple demons, Castiel attempts to rebuild the wall in Sam's mind only to discover that it was destroyed. In one last effort to redeem himself Castiel shifted the hallucinations of Lucifer from Sam's mind to his own in order to save Sam. Castiel then looked on in horror as he could only see Lucifer's face as he is committed to the Mental Institute. Meg becomes a nurse at the hospital to look after him.
In Reading Is Fundamental, Castiel awakens from a coma when The Word of God is released from the clay containing it, but is still insane with an eccentric personality. Castiel explains what the Word is, but is unable to give Dean the answers he seeks and Dean is still angry with him for what he did to Sam. While talking to Dean, Castiel senses other angels and finds Hester and Inias, two angels from his former garrison. While Inias is happy to see him, Hester is furious due to the damage he caused. Before things can degenerate too far, Dean banishes all three angels. Castiel later meets up with the group on the road to Rufus' Cabin and helps angel-proof it. When Meg returns, he confirms her story that she killed other demons, but warns that she has drawn the attention of the angels. Hester and Inias arrive with two other angels, but in his mental state, Castiel is now a pacifist and refuses to fight, even to save his own life. Castiel is nearly killed by Hester, but Meg kills her and saves him. Afterwards, Inias offers Castiel the chance to return to Heaven, but he chooses not to as he no longer feels like he belongs there. Sam and Dean discover from the translation of The Word of God that they need the blood of a Fallen Angel for the weapon that can kill Leviathans and Castiel happily gives them his blood telling them "always happy to bleed for the Winchesters." Castiel then disappears, not sure where he's going next, something he finds amazing.
In Survival of the Fittest, Castiel has Meg bring him to the Winchesters after learning that the Leviathans have killed all of his garrison. Crowley arrives and is furious to see Castiel alive, but leaves him alone as he is insane and he doesn't want to pick a fight with a crazy person. He also leaves Meg alone when Castiel gets defensive of her, telling Sam and Dean that Castiel is vital to defeating the Leviathans. Castiel denies any knowledge of what he's talking about however. After finding out that the Leviathan leader Dick Roman has made multiple copies of himself, Dean turns to Castiel for the help Crowley said he could give them, but he refuses to do anything due to his new pacifism and briefly leaves during which time Meg reveals that due to being the Leviathans original vessel, he possesses the ability to tell them apart and could identify the real Dick Roman. After watching Bobby be put to rest, Castiel takes Dean to retrieve the Impala and explains his reasoning for refusing: he feels that he is bad luck and will cause more harm than good if he gets involved again. He also sees his resurrection as an unending punishment for his actions. Dean finally forgives him for what he did to Sam and Castiel agrees to help, possibly out of loyalty to Dean as Dean believes he will die in the attack. The next day, while Sam rescues Kevin Tran, Castiel and Dean make their way through SucroCorp looking for the real Dick. They dispatch another Leviathan and confront Dick who taunts Castiel about his role in the Leviathan mess. Castiel tries to take Dick on, but is thrown into a wall and easily defeated. This allows Dean to stab Dick with the weapon, but it doesn't work. This causes him to lower his guard and Castiel restrains Dick from behind while Dean stabs him through the neck with the real weapon, killing him. However, Dick pulsates a strange aura and after he explodes, there is no sign of Dean and Castiel.
When Dean wakes up, Castiel, with his original personality apparently back, tells him that they are in Purgatory and are more likely to die then get out. He then disappears leaving Dean alone and surrounded by monsters.
In We Need To Talk About Kevin, Dean escaped Purgatory with the help of the vampire Benny, but Castiel was not with him. Dean later told Sam that Castiel died in Purgatory, that it got hairy near the end and Castiel "let go." While Dean didn't elaborate, this clearly affected him greatly.
Dean had flashbacks of Castiel and it was revealed in What's Up, Tiger Mommy? that he had succeded in his relentless search of finding Castiel. After they greeted, Dean asked if he is sane again, which Cas said he was, or in their case, as sane as he could be, seeing as he an angel in Purgatory. He then told Dean that after their arrival in Purgatory, he actually did run away. This led Dean to believe he left him to fend for himself. Shocked and disbelieving this notion, Castiel elaborated by telling him that the Leviathan want him dead and he had to get them away from Dean by drawing away their attention to protect him. Understanding, Dean accepted his reason but firmly insisted that he would not leave Purgatory without him.
He appeared in another flashback, where he was struggling to hold on to an arm, while it is unclear what the scenario is, Castiel shouted Dean's name as they are pulled apart.
In flashbacks in Blood Brother, Castiel, Dean and Benny come under attack by three monsters and Castiel kills one with his powers. Castiel and Benny try to convince Dean to let Castiel stay away from Dean because as aSeraph he is drawing monsters to him and the way out of Purgatory might not even work for him as he isn't a human or former human like Benny. However, Dean refuses to leave him behind and before they can argue anymore, Castiel senses Leviathans approaching them. Castiel is unable to teleport them out as the Leviathans are too close so they run, but are ambushed by two Leviathans. One manages to defeat Castiel, but before she can kill him, Benny decapitates her, saving Castiel to Dean's shock.
Castiel finally escapes Purgatory in A Little Slice of Kevin. He claims he could not remember how he escaped, a story not received well by a doubtful Dean. Castiel aids the Winchesters and Mrs. Tran in saving Kevin and retrieving the tablet from Crowley. He displays much of his previous abilities, but suffers observable fatigue after using them. Sensing Kevin in danger, Castiel teleports into the room with him and Crowley and confronts his former partner with his Angel Blade. Crowley pulls out one of his own and believes Castiel is bluffing in his clearly weakened state. Castiel displays his wings and goes to smite Crowley who finally retreats, but tries to take the tablet with him. Castiel smashes it in half and Crowley only gets away with one half. The experience causes Castiel to collapse however. After the confrontation with Crowley, Castiel reveals to Dean at the portal that he intentionally wanted to be left behind in Purgatory as a form of penance. Moments after, Castiel finds himself with in Heaven, with another angel. It is then revealed that his escape was orchestrated by the angelNaomi, who sent an incursion that claimed the lives of several angels to aid the seraph. Much to his own surprise, Castiel casually reveals information about the Winchesters and the tablet under the simple request of Naomi. He is then sent back to earth without recollection of the meeting with Naomi and the orders to report into her every so often. He then agrees to help Sam and Dean search for the second half of the tablet and fixes Kevin's cut-off finger.
Castiel formally took up the mantle of being a hunter in Hunteri Heroici. Dean and Sam were skeptical at first, but both eventually allowed the seraph to join them in a case that Castiel himself found. The Winchesters also guided Castiel on how to pose and act as an effective hunter. Castiel also admits that he fears returning to Heaven: he fears that when he returns and learns just how bad he made it, he will kill himself out of regret. While Castiel is awkward and clumsy at being a hunter, he proves very helpful in solving the case, using his powers to bring Sam into the mind of Fred Jones, a man who is living inside his own mind as it is easier than having to live with the real world. Sam gives Fred a speech about living in a dream world and how it can be good for awhile, but eventually you have to wake up and deal with your problems, something Castiel clearly listens to. After the situation is resolved, Castiel offers to remove Fred's powers when he wants to make sure it won't happen again, but warns that it will be very painful and he isn't sure how much of him will be left. Fred agrees and Castiel does the procedure, leaving Fred in a mentally-distant state, but happy. Even though Sam and Dean have come to accept Castiel as a hunter, to the point that Dean offers to allow Castiel to ride "shotgun" in the Impala, something he had previously refused, Castiel decides to return to Heaven to face up to what he has done, but Naomi refuses to allow it and asks him what he wants to do. Castiel decides to watch out for Fred for a few days, but also to stop running from his problems.
In Torn and Frayed, he is shown helping people in need, in repentance for his previous actions. He cures a baby of an inguinal hernia (due to which the baby cries incessantly), which couldn't be detected by doctors themselves. He was ordered by Naomi to rescue a fellow angel Samandriel, who was held captive by Crowley in an abandoned building heavily covered with Enochian sigils that he locates with Dean's help. Castiel gathers the ingredients needed to make a "demon bomb" and retrieves Sam against Dean's wishes, telling them to "stow their crap." During the attack, Castiel gives Sam his Angel Blade to kill demons with and remains outside until Sam and Dean deal with the wards and demons. He was then able to teleport Samandriel to safety, but not before Samandriel revealed to Crowley the existence of an Angel tablet. Outside, Samandriel warns Castiel about this and that "they're" controlling him. Castiel asks who is and who Naomi is when Samandriel brings her up, but before he can explain, Naomi orders Castiel to kill Samandriel, which he does without hesitation. (Throughout the rescue, Castiel saw vague flashbacks of Naomi inserting a certain device into his eye.) Shocked, he demands answers from Naomi, who reveals that knowledge of the angel tablet could cause great harm in the hands of a demon. Under Naomi's orders, Castiel claims he killed Samandriel in self-defense and that he is taking his body to Heaven to be put to rest (in actuality so Naomi can determine how much he broke), but his weird behavior and the fact that one of his eyes starts bleeding draws their suspicion that something is wrong and that he is being controlled.
In Remember the Titans, Dean desperately prays to Castiel to look after Sam who is not doing so well with his trials. Despite Dean's near-begging, Castiel does not appear or respond.
In Goodbye Stranger, Castiel has become so indoctrinated to Naomi's control that he has no trouble ruthlessly killing a copy of Dean and is shown to have killed hundreds of others. He is sent to locate the angel tablet which is in one of Lucifer's Crypts and to stop Crowley from getting it. His interrogation and killing of the demons involved draws Sam and Dean's attention and he arrives in time to save a weakened Sam from a demon that was attacking him. Castiel captures another demon and binds it in a Devil's Trap before claiming to Sam and Dean that he is searching for Crowley's half of the demon tablet and that the demons are searching for a parchment that will allow them to translate the tablet without a Prophet. Castiel tortures the demon for information and after learning the location of the being that is telling the demons where to find the crypts, he kills her before she can reveal the truth to Sam and Dean on Naomi's orders. Castiel heads to the hotel the demon indicated without Sam and Dean and kills all of the demons there before they arrive and they find that the hostage is Meg. Castiel is able to get Naomi to let Meg explain the truth as she could be useful and afterwards bandages her wounds. Meg flirts with Castiel about their kiss in Caged Heat and subtly tells him she wants to have sex with him, something he doesn't catch on to at first but appeared to be willing until he is told to get moving. The group travel to the warehouse where the crypt is located and when Dean orders Sam to stay outside, Castiel tells Sam that he is damaged on a level that even Castiel can't heal.
Castiel later explains to Dean that the damage is all the way down to the subatomic level before they find the crypt. Naomi orders Castiel to throw Dean off the trail or kill him, but he is forced to point out the box with the angel tablet in it to Dean as it is angel-proofed. Under Naomi's control, Castiel attacks Dean and tries to kill him, as he tells her to stop as Dean questions this. Castiel manages to break free at least somewhat before he kills him after Dean tells him that they are family and that he needs him. When Castiel picks up the angel tablet, it severs Naomi's connection with him and all of her control over him and he heals Dean and explains what happened. However, Castiel senses that for some reason he must keep the tablet safe from Dean as well and disappears with it. Naomi later tells Crowley that Castiel is doing what he is meant to do, which is protect the tablet from all threats. Castiel is later seen riding in a bus with the tablet to an unknown location.
In response to Castiel's departure with the tablet, Naomi starts a search for him, trying to enlist Dean's help in Taxi Driver at which time she claims that he is still insane and was simply misinterpreting her orders when he tried to kill Dean. Despite Castiel's behavior, Dean trusts him over Naomi and refuses to believe her as well leaving the hideout unwarded.
In The Great Escapist, Castiel travels between all of the Biggerson's at once, stopping only for very brief periods to throw the angels off of his trail. It is successful until they slaughter everyone in one of the Biggerson's to force him to stop and learn what happened. While he is distracted, Castiel is captured by Naomi, Ion and Esper. Naomi reveals that Castiel has been involved in many atrocities throughout human history, but that his memory of it has been erased because he never follows orders like he is supposed to. Castiel is angry that Naomi would tamper with his memories as sh demands the angel tablet, but Crowley arrives, kills Esper, wounds Ion who is revealed to be working with him and drives Naomi off. Crowley has realized that Castiel is keeping the tablet close to him in case Naomi ever tries to regain control of him again and shoots Castiel in the gut then painfully pulls the angel tablet out of his body. Before he can do more, he gets a call that Kevin has figured out Crowley's trick and Crowley leaves to deal with the problem, leaving Ion to guard Castiel. Castiel pulls the bullet Crowley shot him with out, overpowers Ion and pushes the bullet through his eye, killing him. Castiel later appears on the road in front of Sam and Dean, severely wounded and weakened and asking for their help.
In Clip Show, Castiel is living in the Men of Letters Bunker with Sam and Dean and slowly recovering from his wound. Dean is furious with Castiel and refuses to forgive him for abandoning them again and most importantly, not trusting Dean despite all of Castiel's attempts to apologize. Castiel watches the film they find of a mysterious exorcism and comments that the changed words mean to cleanse or purify. When Sam and Dean leave to check it out, Castiel goes to get them food as they are out, but makes a mess of the store. He gets Dean's favorite beer and porn to try to appease him and also tries to get him pie and is angry and desperate when they are out. Metatron arrives and calms him down and reveals that Heaven has degenerated into many warring factions which Naomi is only the leader of one, not all of Heaven as he had previously believed. Metatron suggests Castiel do the trials to seal up Heaven so that they can lock the angels together and force them to sort out their problems while keeping the war from spilling over onto Earth. Castiel agrees after Metatron reveals that as the Scribe of God, he knows the trials even without the angel tablet and is stunned when the first trial is to kill their waitress Jane (Supernatural) and cut out her heart as she is a Nephilim, the child of an angel and a human. When they go after her, Castiel hesitates as she is an innocent woman, but when she attacks him and Metatron, he kills his niece with his Angel Blade.
In Sacrifice, Metatron reveals that they must get Cupid's bow as the next trial and Castiel asks him about God. Metatron describes him as like one would expect: larger than life, gruff, a bit sexist and eminently fair. As they wait for Cupid to come to make the man, Dwight, fall in love, Castiel goes through personal ads to try to make it go faster by finding him a candidate. While they are waiting, Naomi arrives with two other angels and captures Metatron. Castiel faces off against them with his Angel Blade, but lets them go when Metatron tells him to. Needing help, Castiel goes to Dean who agrees after Sam insists. Castiel and Dean bring the angel tablet to Kevin to translate the last trial and Castiel scares him into doing it when he refuses. As they watch, a woman named Gail approaches Dwight and makes him and one of his regulars fall in love. Castiel prepares to confront Gail while armed, but Dean convinces him to talk first. Gail is worried about the state of Heaven and agrees to give them her bow if they really think they can calm it down, but Castiel must cut it out of her hand. Kevin contacts them to let them know that while he has found the trials, he doesn't see anything about killing a Nephilim or the bow of a Cupid. At that moment, Naomi arrives and though Castiel goes to fight her, she insists she just wants to talk and Dean gets him to hear her out. Naomi tells Castiel that she has learned from Metatron's mind that what he is doing isn't going to seal Heaven up, it will instead expel all angels from it permanently. She expresses remorse for her actions, telling Castiel and Dean that angels were meant to protect humanity and lost sight of that somewhere along the way.
She also informs Dean that if Sam completes the trials he will die as he makes the "ultimate sacrifice" to seal Hell. Naomi offers to hear Castiel out if he really wants to return to Heaven before disappearing. When Kevin can't confirm what Naomi told them through the angel tablet, Castiel doesn't believe her, but transports Dean to the church where Sam is curing Crowley before departing for Heaven. There he finds Naomi dead with her own torture device impaled in her brain and is captured by Metatron who reveals that she was telling the truth. Metatron takes Castiel's Grace as the last ingredient for the spell he is working and sends him to Earth, but not before telling him that he is now human and Metatron wants him to live a human life, die, come to Heaven, find him and tell him about that life. On Earth, Castiel watches as all the angels begin to fall to Earth as Metatron's spell takes effect.
In I Think I'm Gonna Like It Here, Castiel has landed in Colorado and nearly gets run over by a truck. Castiel is left stunned by the cuts on his palms from dodging the truck as he has never experience the types of injuries mortals get before and gets a ride from the driver to a gas station. Reluctantly taking money the driver gives him, Castiel goes to call Dean but meets a Fallen Angel named Hael who is looking for guidance. Castiel suggests Hael take advantage of the new life given to her and go see the Grand Canyon that she claims to have created. Deciding to go with her, Castiel first calls Dean and confirms that Ezekiel is a good guy and can help and then is convinced to come help Dean instead of Hael. She knocks Castiel out and kidnaps him, revealing that she plans to possess him as he is strong and her vessel is weak and deteriorating. In order to stop her, Castiel puts on his seatbelt and then crashes the car, incapacitating Hael while surviving with minor injuries. Castiel takes her Angel Blade and declares his intent to guide all angels in their new lives on Earth, but when Hael threatens to broadcast his location to every angel looking for him if he doesn't say "Yes," Castiel kills her. Later, Castiel starts to dry-clean his bloody clothes at a laundry mat, but needing food and water, steals new clothes and buys candy and a water bottle instead.
In I'm No Angel, Castiel travels towards the bunker, living in homeless camps and trying to avoid angels. After being confronted by and killing an angel one night, Castiel has himself warded against angels being able to locate him with a tattoo. In response, the angel leader Bartholomew sends rogue Reapers after Castiel. While looking for food in a dumpster, Castiel meets April Kelly, not knowing that she is possessed by a Reaper and goes home with her. April cleans the wound he got from the angel he encountered and they have sex, but while searching for his Angel Blade the next morning, she reveals herself as a Reaper, ties him up and tortures him. Castiel tells her how he didn't know about Metatron's spell and that he doesn't know how to reverse it, but that his Grace was the final ingredient and thus he may be the key to the reversal. When Sam and Dean show up, the Reaper kills him with the Blade. After Dean kills the Reaper, Ezekiel takes control of Sam and resurrects Castiel and Dean claims that he made a deal with the Reaper not to kill her if she resurrected him then killed her anyway. Castiel moves to the Bunker with Sam and Dean and is excited by the Bunker's abundance of food and other human necessities and tells a shocked Sam and Dean how he had sex. Castiel sits down to eat, but after learning from Ezekiel that Castiel must leave because the angels are after him, Dean reluctantly tells him so as Ezekiel will be forced to leave Sam and flee otherwise and Sam will die.
In Heaven Can't Wait, while working as a sales associate at a gas station- and also serving as a baby-sitter for his boss, Nora, although he initially assumed that it was a date, Castiel calls the Winchesters for help after two people in his area simultaneously combust. With Dean's aid, Castiel determines that the victims were killed by a Rit Zien, a class of angel healers that kill mortally wounded angels. Castiel then goes on what he believes is a date but it turns out to be a babysitting gig, growing worried when the baby, Tanya, gets a fever and won't stop crying. Before he can take Tanya to the hospital, the Rit Zien, Ephraim approaches him, having detected his pain. Castiel tries and fails to banish the rogue angel, but before Ephraim can kill him, Dean arrives and tosses him an angel blade, allowing Castiel to kill Ephraim. Castiel then goes back to his normal life working at the gas station.
In Holy Terror, Castiel investigates mysterious angel deaths with Sam and Dean. After "Ezekiel" orders him to send Castiel away, Dean does, explaining partially what happened. Feeling helpless, Castiel decides to pray for aid, when his prayers are answered by Muriel, a neutral angel in the war, who explains that the current conflict is between factions led by the angels Bartholomew and Malachi, but the two are captured by Malachi and his ally Theo. Muriel is killed while Malachi tortures Castiel for information about Metatron, revealing that Ezekiel is dead. When Castiel is left alone with Theo, Theo begs him to help him defect to Metatron who he believes Castiel is still working with. Castiel tricks the misguided angel into releasing him, then slits his throat with an angel blade and steals his Grace, restoring his own powers. Castiel then smites Theo and fights his way out. Disgusted with himself but believing it necessary, Castiel calls Dean to warn him that Ezekiel is dead and thus couldn't have been the angel that helped him save Sam.
In Road Trip Castiel, wearing a new suit and trenchcoat, arrives at the bunker to find the main room trashed and a distraught Dean. Dean explains what happened and how he intends to hunt down and kill the angel possessing Sam for revenge even though it will kill Sam. Castiel however, comes up with the idea of having Crowley do the same thing he did to Samandriel to try to bring out Sam's mind, so he can expel the angel. Enlisting Crowley's help, the three take a car that Castiel stole as he can no longer teleport and find the angel. The angel overpowers Dean, but while he's distracted, Castiel knocks him out. After confirming that the angel healed Sam enough that he can finish the job, Castiel watches with Dean as Crowley tortures the angel and follows Dean out when he can't watch anymore. Sympathetic with Dean and forgiving him for kicking him out, Castiel comforts his friend until Crowley calls them back as he has managed to activate the angel's "factory settings." Castiel is furious when the angel identifies himself as Gadreel, blaming him for everything that has gone wrong in the world. However, Gadreel regains control, telling them that he can withstand the torture for a very long time and they can't stop him without killing Sam. Desperate, Dean asks Castiel to possess Sam to make him aware of the situation, but Castiel is unable to as he would need Sam's permission to do so. When Crowley offers instead in exchange for his freedom, Castiel is reluctant, but removes Sam's anti-possession tattoo so Crowley can possess him. The plan works and Sam expels Gadreel. After Crowley returns to his body, Castiel notes the appearance of Abaddon and the three leave Crowley to deal with her. A safe distance away, Castiel heals Sam's injuries from the torture and some more of the damage the Trials did to him telling him that while he will have to do it in stages and over time, he will be able to finish Sam's healing. Castiel stands a respectful distance away as Sam and Dean speak about Dean's actions and remains with Sam as Dean leaves, alone.
In First Born, Castiel is staying with Sam in the bunker and has nearly healed him fully. He is also upset about the fact that he has lost the ability to enjoy human food. However, he discovers that some of Gadreel's grace is still inside Sam and is slowly disappearing every time Castiel heals him. Reading a book and file from the Men of Letters left, Castiel learns that the Men believed that if the grace was extracted, it could be used to track the angel it belonged to. Sam and Castiel begin a procedure to remove the grace, but though it proves dangerous as Sam's body starts to revert to its state before Gadreel possessed him, Sam insists that they continue. With Sam's condition deteriorating as they need more grace then can be safely taken, Castiel chooses to finish healing him rather than take the rest of the grace, destroying the last of the grace inside Sam. Castiel explains that his brief humanity caused him to understand that its not worth it to sacrifice others for the sake of what you need and that he understands where Sam is coming from wanting redemption for his acts as he also wants that, but its not worth his life. Sam and Castiel later use the grace they extracted to try the spell, but it proves not to be enough. Telling Sam that he believes that Metatron is the key to setting things right, Castiel sets out to locate him.
In Captives, looking for information on Metatron, Castiel tracks down a follower of Rebecca, a friend of Metatron's. The follower reveals however that Rebecca had set up a faction called the Penitents who coexisted peacefully with humanity before all but him were slaughtered by Bartholomew and his followers. Leaving the other angel alone, Castiel is captured by angels working for Bartholomew. To his surprise, despite having his angel blade taken away, Castiel is warmly greeted by Bartholomew who was a subordinate and friend of his in Heaven. Bartholomew invites Castiel to join him in uniting the angels, believing that together they can unite all of the angels under one rule. Bartholomew also has the resources to track Metatron when he appears on Earth and offers Castiel his help with tracking him. However, when Bartholomew captures Rebecca's follower, Castiel is horrified by the angel's torture. When asked to kill the angel, Castiel refuses, saying he would rather die than needlessly kill another angel, wanting peace between the angels, not more war. To Castiel's horror, Bartholomew kills the angel then attacks Castiel himself. Castiel overpowers Bartholomew, but declaring his refusal to kill, Castiel lets him go and starts to leave. When Bartholomew attacks Castiel while his back is turned, Castiel is forced to kill him in self-defense. Visiting Rebecca's grave, Castiel is stunned when some of Bartholomew's followers approach him asking for him to lead them in a more peaceful way of existing.
In Meta Fiction, Castiel follows a strange sound to find the Horn of Gabriel and a bunch of dead angels. He finds Hannah alive and heals her, learning that it was Gadreel who killed all of the angels when they refused to join Metatron. Castiel refuses to lead the angels against Metatron and leaves. He is shocked when Gabriel approaches him for help with dealing with Metatron and the two start heading towards the Bunker with Gabriel trying to convince Castiel to help the angels against Metatron, saying that Castiel has been God more than God himself has been. While at a gas station to get more gas for Castiel's car, Castiel and Gabriel are attacked by angels working for Metatron. Gabriel tells Castiel to leave and lead the angels against Metatron while he sacrifices himself to hold the angels off. However, Castiel realizes that it's just an illusion after noticing that a rip in his trenchcoat is no longer there. Castiel proves it by stabbing Gabriel to no effect. Gabriel admits its not real, but that what he said about Castiel needing to lead the angels is true. Before the illusion dissipates, Castiel asks Gabriel if he is truly dead but gets a vague answer in the form of an eye wiggle from the latter. Castiel comes out of the illusion to find himself tied down in Metatron's office in Heaven. Metatron gives Castiel all of his knowledge about popular culture and explains that he wants Castiel to lead the angels against him as he wants Castiel to be the villain in his "story." In return, he offers Castiel an endless supply of grace to replace his stolen burning out grace. Castiel refuses and before they can discuss it anymore, an angel alerts Metatron that Sam and Dean have captured Gadreel. Metatron trades Castiel for Gadreel, blowing out holy fire and easily overpowering Sam and Dean. Afterwards, Castiel tells Sam and Dean he is onboard with stopping Metatron and is angry to find out that Dean has taken on the Mark of Cain. He warns Sam to keep an eye on Dean. The next day, Castiel uses the Horn of Gabriel to call a group of angels to him to become their new leader.
In Bloodlines, Castiel contacts Dean with the information that he has gotten a lead on Metatron causing Sam and Dean to drop the case they are working on and take off to meet him.
In King of the Damned, Sam and Dean meet Castiel at his new headquarters where he is the leader of most of the angels on Earth. He reveals that after he killed Bartholomew and with Malachi dead at Gadreel's hands, all the angels have been turning to him for leadership in the war to retake Heaven. Castiel's men have captured an angel named Ezra who works for Metatron and he wants Sam and Dean to interrogate him. Sam and Dean are able to trick Ezra into revealing that Metatron has an elite ground force and that there is a portal to Heaven that Metatron moves around and controls. Before they can learn more, Ezra is murdered and Crowley calls Sam and Dean to offer the location of the First Blade and Abaddon. Before Sam leaves, Castiel asks him his opinion on Gadreel who Sam believes might have been misunderstood before he murdered Kevin. Castiel sets up a meeting with Gadreel, but comes under attack from two angels that he kills. Castiel later meets with Gadreel again, telling him that Metatron has no honor and asking Gadreel to become his spy. Gadreel refuses due to his own honor not letting him abandon the cause he has dedicated himself to, but Castiel tells him to think on it and leaves.
In Stairway To Heaven, after an angel named Oran kills himself and an ice cream shop full of people including an angel named Ester, Castiel, Sam and Dean investigate. Castiel is stunned as Oran was one of his men and he killed everyone in Castiel's name. Castiel insists that he didn't order the attack though Dean doesn't believe him. While Dean investigates looking for more angels that might be suicide bombers, Castiel and Sam start chasing down a missing angel named Josiah who they come to believe may be the one who killed Ezra and a traitor. During the trip, Castiel is stunned to learn that Abaddon is dead and is worried about the effect the Mark of Cain is having on Dean. Tracking Josiah to Pray, Montana, Sam and Castiel find a building where the door to Heaven apparently is. Passing tests based off of pop culture, they enter a room only to find that its one of Metatron's tricks and that Josiah was caught in a holy fire trap meant for Castiel. Castiel offers to heal Josiah, but he dies rather than owe Castiel his life. Returning to his base, Castiel finds that Dean apparently killed the reaper Tessa who was working for him with the First Blade though Dean tells him that Tessa killed herself. Before they can talk more, Metatron contacts Castiel's followers, offering them amnesty if they abandon Castiel and insisting that Castiel ordered the bombers, only cares about himself and the Winchester and tells them about Castiel's dying grace. Metatron's transmission makes Castiel's followers doubt him and Hannah demands he kill Dean in punishment for killing Tessa to prove himself. When Castiel refuses, all of his followers abandon him. Castiel returns to the Bunker with Sam and Dean where the three become determined to stop Metatron and are shocked when Gadreel shows up to offer his help, confirming that Metatron was behind the suicide bombers and asking for a second chance. Dean pretends to give it to him then slashes Gadreel across the chest with the First Blade, seriously wounding him and causing Sam and Castiel to restrain Dean.
In Do You Believe In Miracles?, after locking Dean in the Bunker's dungeon, Sam and Castiel go looking for Gadreel who has fled in fear of his life and find him. Despite Gadreel telling Castiel not to heal him due to his weakening grace, Castiel does so anyway and Gadreel reveals that Metatron's plan is to convert humanity into worshiping him instead of God. After Sam and Castiel tell him that Dean used the First Blade to injure him, Gadreel insists that Dean is their best chance to kill Metatron and reveals that the source of his power is the angel tablet. Gadreel tells them that if they break Metatron's connection to the tablet, he will be a regular angel again and killable. Castiel decides to sneak into Heaven with Gadreel to find the tablet and has Gadreel pretend that Castiel is his prisoner to get through the portal, getting the idea from Star Wars. In Heaven, Castiel and Gadreel are locked in Heaven's dungeon by Ingrid and Hannah who see through their deception. Castiel tries to convince Hannah to help them stop Metatron, but she refuses to believe him as he promised an end to angel deaths. Gadreel suddenly speaks of his desire to redeem himself being the only thing he focused on since his first imprisonment in the dungeon for thousands of years and how he lost sight of the angels true mission, to protect humanity no matter the cost to themselves. Gadreel warns Castiel and Hannah away and then kills himself, using the same sigil the suicide bombers used to create an explosion to free Castiel. Gadreel's sacrifice convinces Hannah who rejoins Castiel in taking down Metatron. Taking Ingrid captive, Castiel and Hannah try to force her to tell them where to find the tablet, but when she refuses, Castiel orders Hannah to take her out and searches on his own. Eventually Castiel finds the angel tablet in Metatron's typewriter and smashes the tablet, removing Metatron's incredible powers. When Metatron flees an attack from Sam back to Heaven, he finds Castiel sitting in his chair and chains him down. Metatron taunts Castiel with the fact that he has killed Dean, causing Castiel to fail in his attempt to save him by shattering the tablet and calls all angels "sheep" who will follow him where he wants and shows disgust for humanity. Metatron prepares to kill Castiel, telling him that the angels will never believe him because Castiel can never spin a good story. Castiel agrees, saying that Metatron can however and reveals that he has used the equipment in Metatron's office to broadcast the entire conversation over "angel radio." Before a horrified Metatron can react, Metatron's enraged followers storm his office, overpower Metatron and free Castiel. Castiel however locks Metatron in Heaven's dungeon rather than kill him, something Hannah tells him is the act of a true leader. While the angels now once more want to follow Castiel in rebuilding Heaven, Castiel informs Hannah he wishes to be a normal angel again and not a leader. Hannah reminds him that he will die soon when his grace burns out unless he can replenish it, leaving Castiel contemplating the future.
Castiel decides to find the Novak Family and honor his promise to his vessel Jimmy.
After finding Claire in a group home, Castiel tries to make amends but can't get through to her.
Castiel tends to Amelia and comforts her over her husband's death before he goes outside thinking its an enemy. Instead, he finds Dean and Claire who he is annoyed tagged along anyway, despite his warnings. Castiel is thanked by Claire for finding her mother as he and Dean look for Sam and find him in the house where he along with Dean reveal Holloway is a Grigori.
Castiel is shocked as he gives the Grigori's history but states they were destroyed but Sam reveals some of the Grigori survived and have abducted people to create Heavens in their minds before feeding off their souls. Disgusted and enraged, Castiel demanded to know where the abomination was and they arrived to find it killing Amelia who protected Claire. Castiel, Sam, and Dean fought it but were overpowered though Claire took Holloway's (Tamiel) sword and kills him.
Castiel is officially forgiven by Claire and is gives her a present for her birthday while Dean gives her a book on monsters as he realized she wanted to be a hunter.
Castiel is mostly possessed by Lucifer and only takes back control when the latter tried to kill Sam or when they return to Heaven where he pleads to the Angels for aid.
After Amara banishes Lucifer from his body, Castiel regains control of his body and is helped by a relieved Dean.
During this period, Castiel finally meets his father God in his human guise as Chuck Shurley and helps his friends to find a way to beat Amara.
When Billie tried to fulfill her bargain with the Winchesters by claiming Mary's soul, Castiel sneaks up behind the reaper and kills her to prevent any Winchester from dying. He tells them the world needs them and he will not allow them to needlessly sacrifice themselves as they mean too much to him and the world. The family are shocked but touched by the extent of his care for them.
Castiel fights Dagon and is nearly killed but the unborn Nephilim empowers him allowing him to kill the Prince of Hell. This changes his perspective of the child he thought was dangerous, he decided to protect it and allow its birth.
Castiel takes Kelly to her cabin and helps her with getting it ready for the baby. Sometime later, he sees that the baby has caused a rift to form and open to another world which he travels through.
Castiel enters the other world and is surprised by the surroundings which is in complete chaos. He is attacked by the demons there but is saved by the counterpart of Bobby Singer who he gets acquainted with and learned about the other world being locked in a war zone between angels and demon.
Castiel returned to his world and helped Kelly as she prepared to give birth before the Winchesters arrive. Castiel healed Dean and decided to show them the rift and soon the other world and they were shocked by it.
In Lost and Found, after being killed Castiel's body is found by angels who have a different reaction to his death :one believing that he deserved better while the other thinks that he deserved it. After failing to get God to resurrect Castiel, the Winchesters and the Nephilim Jack (Nephilim) burn Castiel's body in the style in that of a hunter's funeral while bidding him goodbye.
In Patience, while Sam and Dean were arguing about him being the indirect cause of Castiel's death, Jack overhears this and his eyes glow as he sadly says Castiel's name. In a black realm, the essence of Castiel is sleeping before he awakens after hearing Jack's voice calling his name. Castiel then wonders as to where he is.
In The Big Empty, Castiel then wandered the mysterious area asking for someone to appear but received no answer as he was followed by an unknown figure. He soon felt the presence of the unknown being and told it to come out. The being appeared to him taking on his form introducing itself, as a "friendly neighborhood" Cosmic Entity as it stated it took on his appearance so that he wouldn't be afraid. The Entity then told Castiel the realm they were in was The Empty, the place which existed long before everything even God and the Darkness. The entity soon reveals the realm is where Angels and Demons go after death and explained to the surprised Castiel that all the inhabitants there are put in eternal slumber and it was sleeping as well but its slumber was disturbed by Castiel awakening. It questioned the seraphim on this but Castiel didn't know, thinking the Winchesters had a role in it but the entity rebuffed this stating only it has power over the realm and pressed him, though received no answer. The entity then looked through his mind to find the source of his awakening as Castiel was put in pain because of it. When the entity stated it wanted to return to slumber but couldn't with Castiel awake, the latter realized having him awake caused it pain and suggested it get rid of him by sending him back to earth. He soon sees through the entity's bluff to throw him deeper in the depths of the realm, as he knows it wouldn't work and demands his release. The entity refused and said Castiel didn't want to return as it read his mind and knew there was nothing on Earth, painfully showing him memories of past.
The entity soon struck down Castiel, calling him worthless as it suggested that he should go back to sleep to forget his failures. However, Castiel refused the entity's demands and stated he would stay awake and keep the entity awake unless he is freed. The Entity denied his demands but Castiel continued to boldly demand for his release from the empty and stared down the entity as he stated this.
Castiel later awakens in a meadow on Earth and realized that the Entity has resurrected him, just as he demanded. Castiel then basks in the sunlight, happy to have been brought back to life.
In Advanced Thanatology, Castiel had traveled to a small town where he had used a payphone to contact Dean who was surprised to hear from him. The Winchesters then traveled to the town and were met with shock, as they are reunited with a resurrected Castiel who greets them with a nod.
In Tombstone, the Winchesters questioned if its really him and he confirms it, stating he annoyed an "ancient cosmic being" to the point that he was brought back. He is then asked if he was in Heaven but he states he was sent to The Empty, which is where Angels and Demons go after they die. After being asked what the realm was like, Castiel describes his horrible experience in the void of nothing and how he was sleeping but he awoke after hearing a voice say his name. Castiel voiced his belief of thinking they had something to do with it but they state it wasn't them, as they didn't think they could bring him back. Sam asked if God had a hand in it but Castiel replies that he has no power in the Empty as the brothers realized it was Jack. The brothers bring Castiel back to the bunker, where he finally meets his nephew Jack who is shocked to see him and questions his return. Everyone learns it was partially because of Jack's begging that Castiel came back to life as he thanks Jack who hugs him. Jack shows Castiel some of his powers and then revealed he was researching and showed the group a case, which he suspected was zombies. While Dean humored him they decided to go through with it and ordered a move out.
On the case, Jack caught up with Castiel about his not being there and that Jack's mother was right about him being good. Jack's research about the case proved correct but it turned out the monster was a ghoul. After finding the monster, Jack tried to help Dean but ended up killing an innocent bystander and fell into a depression. Castiel and Sam tried to comfort him but Jack angrily told them to stop. After Dean killed the ghoul, Jack felt guilty for his actions as everyone tried to comfort him about his pain but he left the group after apologizing for flinging them around.
During War of Worlds, Castiel decided to locate Jack by contacting an angel named Duma who he asks inquires if Heaven had him. Duma denied this by stating if Heaven had Jack, he would be put to work by creating new angels to replenish their numbers following the fall caused by Metatron. Other angels appear and offer Castiel the chance to return to Heaven if he helps them find Jack as he would listen to him but the latter refuses to enslave Jack and fights the angels. When Duma has the blade to his neck, a voice orders her to stop and everyone is shocked to Lucifer back. He orders the angels to back off and they comply after he intimidates them which saves Castiel as the angels retreat to Heaven. Castiel angrily questioned his brother on his return as the latter did so to him and both commented it was complicated. Castiel then tried to attack Lucifer but he was dissuaded otherwise as the archangel told him of a threat. At a bar, Castiel is told by Lucifer that the Apocalypse world has an alternate version of Michael who wants to invade and conquer their world.
Castiel was skeptical even voicing it could be a ploy so Lucifer could get to his son but the latter stated he was telling the truth, as Michael was the one who wrecked the other world. Castiel wanted to involve Sam and Dean but Lucifer tried to dissuade him though was annoyed to hear Castiel lost Jack but pleased to hear he hurt the Winchesters, much to Castiel's annoyance.
Castiel and Lucifer are then confronted by Asmodeus who effortlessly overpowers and captures them. He planned to use Castiel as a way to keep the Winchesters in line while Lucifer was to be used in the conflict with the invading Michael.
During The Bad Place, Castiel is mentioned by Jack to be the one of the few people besides Sam and Dean that he sees as family.
In Various & Sundry Villains, while being held captive by Asmodeus he is told by a demon guard Dipper has plans for him. Castiel soon listens to Lucifer shouting about Michael invasion, Castiel is still skeptical until Lucifer compares the other Michael to their version of their brother which is when he settles on something he does it. Castiel asks about the time they have left as Lucifer says it is short as he remarks on Michael holding Mary Winchester captive and is torturing her which horrifies Castiel. Castiel then stops Lucifer from going on and when that goes on, he brings up some of the good things Jack has done.
After escaping Asmodeus in Devil's Bargain, Castiel searched for Lucifer before collapsing and was found unconscious by a boy who showed his friend. The two mistook him for a corpse and poked him but he woke up which scared them off. He returned to the bunker telling the brothers of his capture and how Asmodeus has his phone to monitor them. He explained Lucifer's return was because of the alternate Kevin Tran and the alternate Michael was intending to invade and conquer their world. He confirmed the urgency because of Lucifer's fear and weak state.
They locate Lucifer and tried to capture him but Anael betrays them and Lucifer nearly kills them though they are saved by Arthur Ketch who forces Lucifer to escape with his accomplice. Ketch offers help since the threats of Lucifer and the invading Michael were too great.
During Bring em' Back Alive, Castiel tends to a battered Gabriel and remarks he is looking awful. As they tend to him, Castiel and Sam see he is showing no sign of change as he refuses to take his own grace to recover. The duo try to figure out how he is still alive and why he won't talk. Eventually, Gabriel uses Enochian language to tell his story in which Castiel translates to Sam and it is revealed Gabriel faked his death at Lucifer's hands as the latter stabbed an illusion while the real Gabriel watched on. With everyone believing him dead, Gabriel was able to hide from others unnoticed by all including God and Heaven who wondered about him.
This act causes Castiel and Sam to see he is still in his right mind. Gabriel later spoke and was given his grace by Castiel. Asmodeus soon called Sam, this worried Castiel as Asmodeus threaten to destroy the bunker for Gabriel.
Asmodeus invaded and Castiel fought several demons and rescued Sam from being killed by one before Asmodeus flung away Sam and Cass before he had his men take Gabriel who is threatened by the demon. As he was taken away, Asmodeus tortured Castiel and Sam until Gabriel broke free of his captors. Castiel watched Gabriel heal himself and killed the demon by incinerating him on the spot.
Castiel caught Gabriel up on everything that transpired such as his new nephew being sent to Apocalypse World and that world's Michael coming to invade. He refused to help and wished them luck in their endeavors as he placed his bet on them before and was right. Gabriel left the bunker later.
In Funeralia, Castiel goes to help in Heaven, he tells Duma and the angels about Gabriel's survival and tells them of the invading Michael. The angels are surprised at these developments and decide to hear him out before Naomi appeared. Surprised to see her but angry, Castiel questioned her survival and learns she faked her death years ago. They talk as he bluntly states his previous relief at her death as she remarks they never did get along and he brings up her actions as she states its in the past. She tells Heaven is going to be destroyed soon, due to the low number of angels and if it happens billions of ghosts will besiege Earth. Castiel was greatly shocked at this revelation as he didn't know there numbers were that low as Naomi tells him his news about Gabriel provides hope and if he brings him back, Heaven can maintain its state.
Castiel and Naomi then travel to Earth as he tells her there has to be a way to stop the problem while she tells him that everything comes to an end and she decides to close off Heaven until he finds Gabriel. Sharing a nod with his sister, Castiel watches as she leaves through the portal.
In Unfinished Business, Castiel is mentioned to be helping Gabriel settle in after he decided to help the Winchesters once they saved him.
In Beat the Devil, once Gabriel and Rowena capture Lucifer and bring him to the bunker, Castiel drains him of his grace to power the rift.
With it open, he, Sam, Dean, and Gabriel head to Apocalypse World and they travel to the resistance's camp. As the Winchesters lead the way, Castiel speaks to his brother and tells him about Heaven and how it may need him.
When Jack is informed of Sam's fate and becomes distraught, Castiel tries to comfort him but he ignores him and questions both his uncles on resurrecting Sam as they tell him they couldn't as they are strong enough. Castiel then watches Sam arrive alive and smiles at him before he becomes worried when he sees him being followed by Lucifer.
In Exodus, Castiel takes part in the interrogation of a resistance traitor by personally torturing him until they get a location. He joins in the rescue of Arthur and Charlie with Castiel, by stopping and killing his Apocalypse World counterpart after sharing words with him.
Castiel later joined in evacuating the resistance through the rift to Earth. When he crossed over, he spoke to Rowena who was prolonging its opening. Afterwards, Sam and Dean crossed over with the two telling him that Gabriel was killed by the Alternate Michael.
During Let the Good Times Roll, Castiel soon joined the Winchesters and Jack in hunting werewolves and they are successful in killing the pack.
When one of the evacuates of Apocalypse world Maggie is killed, they questioned her friend who told them where Maggie's crush works.
Castiel went with the brothers to a store to stop Jack from killing an innocent before a guilty Jack disappeared. They are then alerted of angel radio and spot a figure watching them before they flee the building and are thrown back by a shockwave of glass. The Alternate Michael then appeared and greeted them, as Castiel was shocked to finally meet him in person. Remembering Gabriel's death, he tried to attack but Sam stops him as Michael provokes him but Dean keeps Michael at bay. Castiel then retreats with them back to the bunker.
They return home and find Maggie alive with Bobby and Mary, she is revealed to have been resurrected by Lucifer who also came back.