Mur dell'Ariete, known as Aries Mu, serves as the Gold Saint guarding the first temple of Sanctuary. Born in Tibet and trained under the previous Aries Saint Shion, he mastered powerful psychic abilities. These powers include telekinesis, teleportation across vast distances or dimensions, and advanced telepathy. Following suspicions about Shion's assassination, he retreated to the secluded region of Jamir, accessible only to those with powerful cosmos or psychic energy. He lived there in isolation with his apprentice Kiki, focusing on repairing damaged Cloths for other Saints. This role required rare materials like Gammanium, Orichalcum, and Stardust Sand, often necessitating a significant blood sacrifice from the Cloth's owner to initiate repairs. His initial encounter with the Bronze Saints occurred when Shiryu sought Cloth repairs. Mu tested Shiryu's resolve by demanding the life-risking blood sacrifice but intervened to heal him once sufficient blood was provided. Later, he protected Shiryu from Cancer Deathmask's attack, revealing his identity. During the Sanctuary arc, as guardian of the Aries Temple, he declined to fight the Bronze Saints. Instead, he repaired their Cloths and revealed the existence of the Seventh Sense, the ultimate cosmo level mastered by Gold Saints. He remained behind to safeguard Athena's comatose body. In the Poseidon arc, Mu enforced Libra Dohko's order preventing Gold Saints from aiding the Bronze Saints in Atlantis, though he acknowledged Sagittarius Aiolos and Aquarius Camus for sending their Cloths to assist. The Hades Chapter marked significant development. Confronted by his resurrected master Shion—now aligned with Hades—Mu refused Shion's order to kill Athena. This defiance led to battles against Specters, including the reanimated Deathmask and Pisces Aphrodite. He employed the Crystal Wall to repel their attacks, though Shion shattered it. He forcibly teleported Pegasus Seiya away, deeming the battle beyond a Bronze Saint's capacity, but later relented to Seiya's persistence. Emotionally strained by facing former allies and learning of Taurus Aldebaran's death, he fought Papillon Myu, using the Crystal Net to immobilize him before executing him with Starlight Extinction. His resolve hardened during the Athena Exclamation incident, where he, Leo Aiolia, and Scorpio Milo prepared to unleash the forbidden technique. He later facilitated Virgo Shaka's return from another dimension and safeguarded Shaka's rosary. In the final assault on Hades' castle, Mu fought Wyvern Rhadamanthys despite diminished strength, allowing the Bronze Saints to advance. Beyond the main series, in Episode G, he aided Leo Aiolia by repairing his Cloth and fending off Titan soldiers, later teleporting Taurus Aldebaran to Greece to rescue allies. The Lost Canvas epilogue showed him reporting to Libra Dohko about Athena's reincarnation. In Legend of Sanctuary, he maintained a pacifist demeanor, using Crystal Wall defensively against Seiya without intent to harm.