Aries Mu (牡羊座のムウ Ariesu no Mū?) is very soft spoken, with a scholarly-like personality; his demeanor is very tranquil and logical, almost as if he is a professor of the Sanctuary. Various official translations of the manga and anime, as well as Mandarin language Saint Seiya fans, tend to refer to the character as 'Lord Mu' or 'Mister Mu'. He is good friends with Taurus Aldebaran, and is very respectful to the 243 year old master Libra Dohko. Throughout the manga and anime series, Mu is the man to go to when a Saint needs his or her cloth repaired.
Although every individual Cloth has the ability to regenerate itself after a battle, a hands-on restoration from Mu is needed if a cloth has been severely damaged to the point of death. In normal cases, 1/3 of a person's total blood supply is required for Mu to begin work right away. When restoring an armor, Mu uses hardware tools and the elements that are used to forge a Cloth: the mythical and extremely rare metal known as Gammanium, used in an alloy with the legendary metal Orichalcum, and finally, the radiant Star Dust Sand.
While Mu is depicted as a pacifist throughout the first half of the series, he is an extremely capable and powerful fighter when the situation demands so. Not only is the Saint of Aries built with two offensive and one defensive attacks, he is also a master of various psychic techniques. From basic teleportation to advanced telekinesis, Mu is revered as a premiere psychic user among even those outside of Sainthood.
As Mu possesses extraordinary psychic and telekinetic abilities, he can manifest his mental prowess with the Glamour Illusion, a technique he has used only once to date, in vol. 5 of the manga, against the group of the Silver Saints Lizard Misty, Hound Asterion, Kaitos Mozes and Kentaur Babel. The Illusion tricks the opponent into thinking whatever Mu decides, make the opponent think white is black or glass is diamonds, as Cygnus Hyouga described it. Mu used it to trick the Silver Saints into thinking the Black Saints they killed were the Bronze Saints. However, an opponent with a strong mind or psychic power can be capable of seeing through the Glamour spun by Mu, as Lizard Misty was able to discover Eagle Marin's and Mu's deception after some time.
His defensive techniques are Crystal Wall (クリスタルウォール Kurisutaru Wōru?) which creates a transparent, glass-like barrier made of psycho-power, between Mu and an object. The wall is very durable, and has been shown to shield Mu against everything from normal cosmos attacks to poison scent and rebounding the attack back to the enemy with the same strength it was launched. The strength of the wall is dependent on Mu's cosmos level; at 100%, it is nearly unbreakable to almost all but Mu's mentor who taught him the technique, Aries Shion. A variation of this technique is Crystal Net (クリスタルネット Kurisutaru Neto?) that creates a psycho-power made spider web. This web can refrain the movements of the targets that get in contact with it.
Starlight Extinction (スターライトエクスティンクション Sutāraito Ekusutinkushion?) its a teleportation-based offensive technique. Although it essence rely not on destroying the opponent but on removing him from battle, by teleporting the opponent out of sight and out of the fight, when Mu used it against Pegasus Seiya, he was able to send the bronze saint to a location of his choosing. He also used this technique to send Cancer Deathmask and Pisces Aphrodite to Hades' earthly castle in Germany (it must be noted that he was trying to kill them by sending both to the "dead world"). In the fight against Papillon Myu, at the end of the battle when Papillon is entrapped by Crystal Net, Mu sent him out of existence, and thus successfully killed him. (The kill was confirmed by Virgo Shaka's 108 Rosary. The number of the black beads also includes Papillon's.) In Episode G, Starlight Extinction is also used to remove Dimension Iapetos' dimensional rifts.
One of Mu's most powerful attacks is Stardust Revolution (スターダストレボリューション Sutādasuto Reboryūshon?). Like Crystal Wall, it is an attack that was handed down by his mentor Aries Shion (The former Aries Gold Saint and the real Pope of Athena's Sanctuary in this modern era). The attack summons stardust from stars and galaxies then throws million of blows instantly. It's well known that the attack has force of shooting stars and comets and obliterates an enemy with raw cosmos power. In Episode G, Mu used this attack to destroy all the hundred arms of the Hechatonchire.
In addition to all of these techniques, Mu is also blessed with the speed of light that all Gold Saints possess due their mastering over the 7th sense. He can also teleport his own body or any object at will at anytime, even during the midst of battle. The will of Athena wakes Mu and the other eleven gold saints out of death state in order for them to batter down the Wailing Wall.