Aries Mu was a gold saint in the XX Century. He is not a human, but a muvian.
As a muvian, Mu has eyebrows in circle form. His pink hair is long, and his body is a bit beefy. He has a long pigtail.
Mu become the Aries Gold after the training given by the pope Shion (that was the ancient saint of Aries, but become the pope, and Mu used his cloth without user). When Shion was dead by Saga, Mu knew about this, and perceived Saga was disguised as Shion. But, to the gods like Zeus (that give the Earth to Athena, and is a Saga enemy) test Saori to see if she is the true Athena, with Nike, Saori must defeat Saga; so, Mu don't interfered, and lived in Jamir, where continued hidden and only fixing cloths. Kiki become his student, and he taught to Kiki how fix a cloth.
Mu fought against the Titans in this manga.
Mu met Shiryu when he went to Jamir to fix the Pegasus and Draco clothes. After Shiryu gives his blood to these cloths, Mu fixed them and order Kiki to go to the Mount Fuji to give the Pegasus cloth to Seiya, and after the recovery of Shiryu, his guide Shiryu with Draco cloth to Mount Fuji's too.
After Ikki's surrender, Misty destroys a bit of the Mount Fuji with an eruption and Mu teleports the black saints with Seiya, Shun, Hyoga and Shiryu, to cheat the silver saints that he knew they should come to Japan, to kill Seiya, Ikki, Shun, Hyoga, Saori and Shiryu to fight in the Galactic Wars. In the battle with Misty, Mu leaves the Japan and bring Kiki to Jamir, to allow Seiya fights alone and became strong.
Mu goes to Rosan to saves Shiryu's life of Deathmask, that almost sent him to Yomotsu.
IIn the 12 Temples invasion, Mu was called to protect the Aries temple, but he besides leaving Seiya and the others go, repaired his clothes. He continues in the Aries temple until the Victory of Seiya, and after Saori proved to be Athena, Mu swear loyalty to her. But, hewants, she lives a girl normal life until the battle against Hades.
Mu goes fight against Kyoko with Kiki after the 12 Temples Battle.
Mu stayed in the Sanctuary and ask to the Bronze Saints attacks Poseidon Empire, because the gold saints must wait the fight against Hades
Mu has most participation in this arc. He shows his attacks and skills, technique in the first time, because now, the Hades war is the war that the gold saints must fight, so, Mu don't just watch the battle like before, and fought too. Because this, Mu teleports Seiya to Star Hill, to avoid him fight, because he must not hunts battle nevermore.
Shion revives of the deads, and ask to Mu bring the Athena's head in 12 hours; Mu refuses, so, must be killed by his Sensei for disobedience. But, he kills Aphrodite and Deathmask before the punishment, and now, Shion can kill him, so, the revived saints were killed. But, Saga, Camus and Shura appear there and Shion paralyzes Mu to allow them cross Aries Temple. Mu noted bloody tears in the Saga, Camus and Shura hearts. When Shion would kill Mu, Dohko appears and undoes the Shion's paralysis, and ask to Mu to cross the 12 Temples and stops Saga's and his comrades invasions, while Dohko fight against Shion (Shion was not a true villain, so, he hesitates to fight against Dohko).
In the Taurus Temple, Mu finds Aldebaran dead, and Niobe attacks him. But, his crystal wall protects Mu, and Mu just goes to the Gemini House, because Niobe is already dead.
In the Cancer Temple, Mu fights against Myu, and defeats him.
In Virgo temple, in anime, Mu stops Aiolia, and allow Saga, Shura and Camus kill Shaka, because is it Shaka's wish. In the manga and anime too, he uses the Athena Exclamation with Milo and Aiolia, to try dealing with the Athena Exclamation of Saga, Camus and Shura, and Shiryu uses his Cosmo to save the Mu's side of the collision of the two Athena Exclamations.
After the 12 temples battle, Mu goes to the Hades castle, and, was defeated by Radamanthys, because the barrier of the castle, removes 90% of the energy of a non-specter.
In the Meikai, he gets the eighth sense to revive and try vainly break the Wailing Wall. After Saga, Aiolos, Aldebaran, Shura, Camus, Aphrodite and Deathmask resurrection, Mu with all the gold saints, sacrifice his life to destroy it
Soul of Gold
Mu was revived by Odin, but Odin doesn't tell him, because Loki must discover it over and aborts his scheme (he thinks he revived the gold saints). So, Mu tries discovery why he was revived, and in a village, met a boy that his family was kidnapped by Fafner, to his text. Mu allows Fafner kidnaps him, to spy what Fafner must be doing, and discover a seed in Yggdrasil.
After Aphrodite says to him about the origin of the barrier, he helps Milo, Aiolia and Aldebaran destroy it. In Yggdrasil, his fight with Fafner again, but Deathmask ask to Mu leaves the battle with him. In Andreas's room, Mu uses the Athena Exclamation to kill Loki and Yggdrasil, but was in vain, and Mu is absorbed by their roots. Mu was saved by Aphrodite, and helps Aiolia to kill Loki.
In the fourth movie, Mu was killed by the death angels of Lucifer.
In the fifth movie, Mu was imprisoned by the Olympian Gods, that was allied of Athena in the Saga rebellion, but he thought Athena would not fight with Poseidon after the Olympus decides that Earth must be destroyed, so, they arrested the gold saints that help Athena fight against the gods.
In the sixth movie, Mu probably was a Saga servant, but when Saori arrives there, he recognizes her as Athena and help she, caring of her hurts.
As a muvian, Mu can teleports him and another people, and have telekinesis and telepathy powers (the strongest of the Athena's arm), and creates crystal objects, like a web (that can arrest the enemy) and walls (in the manga, this wall is solid and reflects enemies contacts and attacks; in the anime, this wall is made of waves) and can fix clothes.
As a Saint, Mu uses his cosmo to make starforce explosions.