In the TV series
Heather is the daughter of Oswald the Agreeable and sister to Dagur the Deranged. From a very young age, she was separated from her real family, and was eventually taken in by a couple who raised her as their own daughter.
Riders of Berk
Heather is first found by Snotlout under a wrecked boat and he quickly alerts the other riders. Heather acts frightened at the first sight of them. She tells them that pirates attacked her family's ship and were laying siege to her island. While trying to figure out a way to help this new stranger, Hiccup and his father agree to let Heather stay at their house for a few days.
That night, however, Astrid notices Heather spying on her and Stormfly, and thus grows suspicious of the newcomer. The next morning, Hiccup is trying to find a way to make Toothless achieve a greater speed. Heather suggests he should use a shorter connecting rod, which would push the rider back in the saddle more, making them more streamlined. Hiccup thanks her for the idea. While the two tested it out, Hiccup ends up missing his meet up with Astrid. After they arrive at the Academy, Heather taunts Astrid, asking her is she slept well. When Fishlegs reveals the Book of Dragons to Heather, Astrid snatches it away from her eyesight and then tries to warn Hiccup, but Hiccup doesn't buy into her suspicions.
Heather soon starts digging for information about the academy dragons, even resorting to flirting with Snotlout so he will tell her more about Hookfang and his abilities. The only dragon species Heather can't find anything on are Deadly Nadders so she snoops through Hiccup's room for the Book of Dragons to see if there is anything useful on there. She ends up getting caught by Astrid but somehow manages to excuse herself to Hiccup by putting on an innocent act. Astrid then informs Hiccup about seeing Heather sneaking around during the night but Hiccup still remains unconvinced by Astrid's suspicions.
Heather then sneaks off to Stormfly's pen and tries to gain her trust by feeding her chicken. Astrid catches her again, but this time Heather doesn't use her "innocent routine," saying Astrid was too smart for it in a cocky manner. She further pushes her buttons when even Stormfly was taking a liking to her.
Later, when Stoick and Hiccup are clearing the table, Heather goes for the book under Hiccup's bed. However, Hiccup has it with him, leaving her annoyed. Heather then makes her way to the beach, unaware that Astrid, who was in the forest venting, is following her. Heather meet up with Savage, revealing that she is working with the Outcasts. She tells him that the Riders have a book with everything they know about dragons though she isn't in possession of it yet. Begging for more time, she tells Savage she will get it. Astrid accidentally knocks over some pebbles, alerting Heather to make her way back. Astrid tries to warn Hiccup again with what she just discovered, but when they rush upstairs Heather is already in bed, pretending to have been asleep the whole time.
The next morning Heather not only makes it off with the Book of Dragons but Stormfly as well. Hiccup, finally realizing that Astrid has been speaking the truth the whole time, gathers the Dragon Riders together to chase Heather down. Astrid manages to jump onto Stormfly's back and the two girls end up in a physical fight over the Book of Dragons. As they cross into Outcast territory, Astrid knocks Heather off along with the book. Snotlout catches Heather in his arms while Hiccup tries to save the Book of Dragons. However, the Outcasts fire at him and Toothless, forcing them to retreat. This leaves the Book of Dragons in the hands of Alvin the Treacherous. The next morning, Heather not only makes off with the Book of Dragons, but Stormfly as well. While she tries to fly her, Heather is unskilled at dragon riding, moving in a sloppy manner. Finally convinced, the Dragon Riders chase, and soon catch up to her. Astrid manages to jump onto Stormfly's back and the two girls fight for her and the book. When they cross into Outcast territory, Astrid knocks Heather off, along with the book. Snotlout catches her while Hiccup tries to grab the book. However, the Outcasts fire at him and Toothless, forcing them to retreat. Leaving the Book of Dragons in the hands of Alvin the Treacherous.
Heather is then locked up in Berk. She tries to break out of jail and run towards a boat but Astrid catches her. After being thrown back in her cell, Heather reveals that the only reason she worked for Alvin was because he had her parents. When Astrid brings up her pirate story, Heather admits to lying and putting on an act. She explains the only reason she did it was because she needed the Riders to trust her, but Astrid is doubtful and tells Heather they no longer trust her.
Astrid ends up disguises herself as Heather as a part of the plan to get the Book of Dragons back. She sails off towards Outcast Island by herself with Hiccup and the others as backup. While Heather in the meanwhile successfully manages to break out prison. She ends up escaping with Stormfly again but this time with the intention of helping the riders. Astrid manages to retrieve the book and rescue Heather's parents in the process once she learns that Heather was telling the truth. When Heather finally arrives to Outcast Island, she helps the riders fight Alvin.
Some time later, Heather's village was attacked by Dagur the Deranged. After that, she found and trained a Razorwhip, naming her Windshear.
Race to the Edge
Three years after the end of The Berserker War, one of her raids was spotted by Bucket and Mulch, thus drawing attention of Berk's Dragon Riders and was tracked back to her camp. One by one, she incapacitates them until only Hiccup is left. After a chase, Hiccup corners Heather and she reveals her identity. She explains she only did it because she had made a lot of enemies and she didn't want the Riders to get involved. After clearing things up, Hiccup and the riders invited her to stay at the Dragon's Edge. When they asked how she trained a Razorwhip, Heather explained it was because of training the Riders showed her. After telling them how she and Windshear met, they soon noticed a more intense side to Heather. While this worried Hiccup, Astrid enjoyed it. Later that evening, Hiccup asks why Heather was attacking ships, but she just tells him not to worry, though Hiccup is. She tells him that a lot has happened in the last few years, how everything had changed for her. Hiccup is still surprised by her change, even unsure it's the real her. Heather is about to tell him what happened, but shrugs it off. Hiccup assures her that the others are there for her. Heather thanks him for being a great friend.
That night, Heather locks the dragons in their pens so she can't be followed. Unknown to her, Hiccup and Toothless are not far behind. She then meets up with Trader Johann to get the information she's looking for. Heather then heads out to find Dagur, to get her revenge for her parents and village. However, Dagur was not traveling alone, and used the chains from the Reaper to capture her and Windshear. Thankfully, Hiccup and Toothless arrive in time and blast the winches, freeing them. While Heather wants to stay and fight, Hiccup convinces her to retreat for Windshear's safety.
On the way back, Hiccup explains that he knows Dagur wiped out her village and tries to tell her she doesn't have to do everything alone, though Heather tells him she feels destined to be alone. She admits to him she was actually separated from her birth family at a young age. All she could really remember was her father's hands and the smell of his shield he let her play with. She also tells him her horn was given to her by her birth father, wishing to know who he was.
After arriving back at Dragon's Edge, Heather apologized for locking up the dragons, thinking the Riders wouldn't let her go if they knew what she was up to. The Dragon Riders bury the hatchet, saying Heather was one of them now. Once again, they, excluding Hiccup, swoon over her, but Astrid pulls her away for some girl time.
The two quickly bond at target practice. Astrid still wants Heather to show her how she made her axe. Heather then asks if Astrid and Hiccup were a couple, throwing Astrid's focus off. She explains that they are just friends, but Heather doesn't buy it. Astrid then pokes about her and Snotlout, though Heather says she likes a little smarts, like Fishlegs. Astrid teases this, finding it hard to believe. The girls move on to another activity, jumping of cliffs and grabbing on to their dragons. Astrid makes it, but Heather misses, though Windshear catches her in time.
Heather decides to show Astrid something at her camp. There they meet up with Johann, who was worried about Heather as she was not around. The two explain that Johann is Heather's informant on Dagur. He tells them that Dagur is about to make a deal for some new ships with anti-dragon catapults and grappling hooks in the Sea of Despair. After the deal is done, Johann won't be able to find him again. Heather and Astrid head back to the dragon camp for reinforcements, but the Riders are unsure as Hiccup and Toothless, who have headed to Berk, are not there, even Astrid. Heather is hurt by this, thinking that all they had said about having her back was just talk. But before she leaves, the others have decided to join her, as long as it was just a capture mission. Heather agrees, saying they'll sink Dagur's armada and throw him back in prison on Outcast Island. Astrid leaves the map for Hiccup to find so he can meet up with them later.
When they arrive, the twins, Snotlout, and Fishlegs distract Dagur's crew, while Astrid, Heather and their dragons sneak aboard. The two quickly capture Dagur, and when Heather tells Windshear to finish him off, Astrid protests, but Heather has changed her mind, as Dagur didn't capture her village. He is able to tell Heather something, but she gags him, giving the signal to Windshear, only to be stopped by Toothless' blast. Hiccup arrives, trying to tell Heather not to do this, but she isn't shaken, until he tells her his father's seal is caved into Heather horn, which he found earlier. He explains that years ago, Stoick gave it to Oswald the Agreeable for his newborn daughter, telling her he was Heather's father, as well as Dagur's father. Heather is horrified, realizing that Dagur the Deranged, the person who destroyed everything she had, is actually her very own brother!
When the rest of Dagur's fleet shows up, Hiccup tells Heather they need to go, but she is still in shock. Dagur offers Heather to join him, as he's the only family she has left. He even tempted her by saying he knows she feels the Berserker blood flowing through her veins. She gets to her feet, grabs her axe, and leaps over Dagur onto Windshear. She glares at him, unable to accept him as her brother, but still spares his life.
That evening, Heather begins packing to leave. Astrid tries to convince her to stay, where she'll be safe and have support. Heather refuses, as she has a lot to figure out. Heather thanks Astrid, saying it was great to have a friend again before taking off.
Heather returned when she was on the Dragon Hunters' ship. Thinking she was captured as well, Astrid tried to tell her to run, but surprised when Dagur showed up. Heather claimed to have joined her brother and the Dragon Hunters. The next episode, Astrid was furious at Heather for betraying the Riders after all they had done for her. Heather decided to join Dagur as he was the only family she had left, and said he would never hurt her. When the Dragon Riders escaped, Heather confronted Astrid when she was trying to save Stormfly, which she appeared to be victorious. When Dagur came up with the idea to throw the riders overboard, Heather insisted they use them for work and take them to Viggo, which Ryker agreed too. While Dagur was mad at Heather for turning down his idea, she said she did it to protect him. If the riders escaped, Ryker would be blamed and not Dagur. To this Dagur happily said she was his sister.
When Hiccup and Snotlout gave the others a chance to escape, Heather took on Astrid, instead of letting two Dragon Hunters. Though a quick scuffle, Astrid knocks Heather off her feet, and again races to Stormfly. Heather follows her, pulling out her axe while Astrid grabs Stormfly's chains. Appearing to have been beaten, Heather returns to Dagur and Ryker, who then latter claimed they were closer to the Dragon Eye.
In their next encounter, Heather was found camping out in a snowstorm on Glacier Island. Astrid soon found her, and while they and their dragons, stood off, the two soon hugged, revealing Heather was not actually working with the Dragon Hunters, but spying on them. She even sent Dagur on an impossible quest to find another Dragon Eye. It was also Heather who gave the information to Astrid about them coming to Glacier Island and not Trader Johann like she claimed. Heather told Astrid about a cave where she believed the Snow Wraith was hibernating and planned to keep Ryker as far way as possible. Though Astrid was uncomfortable about keeping this a secret from Hiccup, since she never lied to him. But Heather insists to keep the other riders in the dark, knowing Hiccup would want to pull her out.
Heather tried to convince Ryker to search the coast, but he still insisted on checking the caves. Heather purposely revealed their location to the Riders, and saved Hiccup from being shot at by a Hunter by knocking him out. Ryker confronted Heather about this, but she protested that Hiccup was more valuable alive than dead. Getting an idea, Ryker then command Heather to use Windshear to trapped the Dragon Riders in the cave, which she hesitantly agreed to. After the Hunters captured the Snow Wraiths, the Riders manages to take them back to relocate, while Hiccup went after Heather and Ryker. Hiccup was about to shoot them down, forcing Astrid to tell him that Heather was on their side, giving her a chance to escape. Astrid explained, back on Dragon's Edge, that Heather only got close to Dagur so she could avenge her family. When she found about about the Dragon Hunters, she continued the charade to find a way to taken them down as well. According to Heather, the leader of the Dragon Hunters was not Ryker, but a man named Viggo Grimborn, whom everyone was afraid of. Since Viggo stayed in the shadows, Heather planned to work with the Hunters to draw him out.
Heather joined in the attack seize Dragon's Edge while trying to give Ruffnut a chance to escape. During first part, she pretended to see and get caught in an ambush, sending one of the search parties running. Heather had Windshear shoot a spine at Ruffnut's head, so she could get free and take Windshear to get backup. Though while doing this, Ruffnut head butted her. When Hiccup and the others showed up, Heather used her horn to call Windshear back.
During another attack by Hiccup's Riders, Ryker begins to question Heather's loyalty. During the raid, she has Windshear fire at Snotlout and the twins to make the fight believable. She even had Windshear take a spike from Stormfly. When Ryker confronted her, Dagur defended her, much to Heather's surprise. Then one of the Hunters gave a message to Ryker about regrouping with Viggo. Heather asked Dagur what he knew about the Dragon Hunter leader, telling her he was very clever and that everyone was afraid of him, even his own brother. When Dagur joked about having family conflict, this made Heather slightly nervous.
When Heather, Dagur, and Ryker met Viggo in his tent, the leader began to talk about a game called Maces and Talons, using it as an example about trust and trickery. During this moment, one of the Hunters was brought in for taking some goods. Surprisingly, Viggo spared the man, and sent the others off to get some rest, except Heather. He told her about his knowledge of a traitor, questioning if it was Dagur or Ryker. He then told Heather of his plan to capture a Flightmare.
Heather later met up with Astrid and Hiccup about the plan. She gave them a map that she used to track the Mystery Class dragon, also telling them it was going to be just her, Windshear, and Viggo. The three planned an ambush to take out Viggo for good. However, when Heather and Viggo arrived to the island, she discovered Viggo already knew she was the traitor, and sent his fleet to the island. After fighting off several Hunters, Heather and Windshear joined the Dragon Riders. But when the Flightmare was captured, she tried to save it. This led to her and Windshear being caught as well.
Later, Heather tried to reason with Dagur into letting her go, since they were family. Though Dagur refused, even argued about how she tried to kill him before. Heather explains she didn't know they were siblings at the time, and that he also had wiped out her village. While this does cause Dagur to think for a moment, he still locks her up.
After a conversation with Ryker, Dagur leads Heather, along with two guards into a cave, then knocks the Hunters out. He then frees Heather and reunites her with Windshear. The two do not speak, as Dagur walks off. Heather then helps Hiccup and Astrid redirect the Flightmare away from the island. However, she and Windshear disappear afterwards without a word. However, she became pen pals with Fishlegs via Terrible Terror air mail.
Heather then returned to the Edge. There, She and Fishlegs became closer. However, Meatlug attacked Windshear when she got jealous of Heather. Heather then decided to leave, but then stayed when she and Fishlegs switched dragons. Heather then joined the Dragon Riders and stayed at the Edge.
Heather quickly became an asset to the team. When Hiccup and Toothless were captured by the Hunters, she used her knowledge of the Hunter ports to find them. She helped free them, along with the other dragons that had been captured.
When the Riders took in a baby Death Song named Garffiiljorg, Heather showed sympathy for the dragon instead of being annoyed by its cries like the others. She refused to abandon him, knowing what it was like to be alone. She sang to Garff, which lulled him to sleep. This gave her and Hiccup the idea to sing to Garff to train him. This did not work out as planned, so the Riders decided to take Garff to Melody Island, hoping her would bond with the Death Song they have encountered previously. They were soon trapped by the Mystery Class dragon, who also reject Garff since he was singing the songs the Riders taught him. After trying to find another song the Death Song would like, he bonded with Garff. Heather encouraged him to go off with his new family.
Heather, Astrid, and Snotlout followed Viggo's ships to find out what he wanted with a large supply of marble bricks. They soon discovered Viggo was using them to make a dragon proof fortress on his island. With it nearly complete, they raced back to warn Hiccup and the others. Fortunately, they had rescued two Catastrophic Quakens, which were used to mine the marble, and had them destroy the base.
One night, Hiccup brought up Dagur at dinner, and asked the others about the possibility that he had changed. Heather quickly shrugged this off, and even threatened to split Dagur in two if she saw him again. Hiccup sent her and Snotlout out to scout Viggo's fleet for a mission to destroy it, to prevent Heather knowing Dagur was actually on Dragon's Edge. When they got back, Heather saw Dagur and immediately thrusted her axe at him, but stopped just inches away, though she did punched him. Heather berated Hiccup for teaching Dagur to ride a dragon. Hiccup tries to explain how Dagur had saved him and Toothless, but Heather stilled believed that he was working for Viggo. She even told the others it was Dagur's fault she was separated from her family, and her anger at him for killing their father. As Dagur leaves, he finds Hiccup's display for Viggo's fleet and tries to warn them it's a trap. At this point, no one believed him and he agreed to be locked up. The next day, Dagur broke out with his new dragon Shattermaster and headed toward the armada. Heather tried to knock him out of the sky, but he managed to subdue Windshear long enough to prove it was a trap, and took on the entire fleet himself, but cost him his life. While the other Riders were mournful of Dagur's death, Heather did not share their grief, believing her brother thought he could make it out alive. Hiccup comments that he never heard Heather call Dagur "brother" before, which causes her to head back to her hut. Once there, she found a note from Dagur, in which he apologized for everything he had done. He also told Heather about Viggo's dragon auctions. The note also reveals that Dagur didn't kill their father, but that he actually went missing. Heather begins to cry, finally forgiving Dagur, and mourns his death.
Heather and the other riders then infiltrated Viggo's Dragon Auction. However, they were briefly captured by the Dragon Hunters. They were then saved and freed by Grump They were then able to free all the dragons. Heather and the other riders were then sentenced to death by Defenders of the Wing's queen Mala for allowing the Eruptodon to be taken by Dragon Hunters.
Heather has green eyes and long black hair that frames her face with her bangs parted on the right side and a braid placed over her left shoulder. She also seems to wear some form of eye liner in the first season. In Riders of Berk, Heather wears a light gray shirt that goes halfway down her forearms with a leather vest over it, a hollow horn around her waist and an off-white skirt underneath. She wears brown pants, wristbands, and boots with roping. All of her clothing has patches.
On School of Dragons, Heather wears a long white, sleeveless tunic, similar to a lab coat, with round, metal shoulder pads. Around her waist is a yellow belt with with small pouches on the sides. She wears a light brown, long sleeve shirt underneath, brown bracers, green pants, and brown fur boots. Heather also has a pair of goggles on her head and carries a long magnifying glass.
Heather's appearance has a drastic change in Race to the Edge. She now wears a black, short sleeved hooded shirt, and a brown mask to hide her identity. She also has a brown leather vest, dark gray pants, and brown boots. She has three black belts, as well as one that holds her horn and a lens for the Dragon Eye. Heather has metallic-like shoulder guards, bracers, knee pads, and skirt, all from the scales from Windshear. Heather still wears her hair in the same style as before but it is noticeably longer. She no longer wears eye liner.
Heather also possesses a satchel similar to the ones the other riders use, except it is black in color and has no crest on it.
Heather is perceptive and able to think her way out of trouble. She is also willing to go to great lengths to help her own cause.
Heather often comes across as two-faced, sly and untrustworthy, and has herself a hard time putting trust in others. She is deceitful and fickle by nature, prone to being secretive and lying to people that proved to be worthy of her trust. While not easy for her, she is also willing to abuse the trust of her friends and hurt them (emotionally at least) to further whatever agenda she has, which often ended up putting the Riders at risk. She could also go as far as to put innocent people she didn't know in danger, seen when she tried to deliver the Book of Dragons to the Outcasts (who would have undoubtedly tried to use trained dragons to destroy Berk), even though she did it to save her adoptive parents. She has also shown to mislead and guilt-trip her friends for personal gains.
She seems to take pride in her abilities with deception, maybe even to the point of hubris. She gloated to Astrid about how she was able to win the favor of her male friends and her own dragon, Stormfly. However, she might have done it to merely keep up appearances.
After losing her adoptive family, she is less emotionally stable and often makes the wrong choices, even if is for what she personally believes to be the right reasons. This shows that the loss of her family unhinged her a little bit. She had even persuaded Astrid to lie to Hiccup, which the Berkian had never done before.
Heather is also somewhat spiteful and prone to holding grudges against people, like her brother. Nevertheless, she was able to overcome it in the end.
In spite of all her problematic behavior, Heather has a strong moral drive. She ends up becoming a vigilante for justice by returning stolen loot from pirates to their rightful owners. The main reason she hadn't wanted the Riders to join her mission was to keep them out of trouble. While nervous around dragons at first, after her brief stay on Berk, followed much later by meeting Windshear, she ended up developing an interest for them. It lead her to becoming determined to protect certain species, such as when she wanted to help Garf back to his family and take down the Dragon Hunters for good.
Heather is also very observant, thus very knowledgeable. She asks Astrid if she and Hiccup are together when she notices how close they are.
She has also shown a caring side, as when she sang to the baby Death Song and calmed him, refusing to let the Riders just abandon him, knowing what it was like to be alone.