Mur dell'Ariete, originally named Mu, serves as the Gold Saint of Aries, wielding psychic powers and specializing in cloth restoration for Athena. Born in Tibet on March 27, he trained under the previous Aries Gold Saint and Pope, Shion, inheriting the Aries Gold Cloth. Following Shion's death and harboring doubts about the Sanctuary's leadership, he retreated to the remote region of Jamir, accessible only to those with high cosmic or psychic energy. He lived there in isolation with his apprentice—or adoptive younger brother in some adaptations—Kiki, dedicating himself to repairing damaged Cloths. This work demanded rare materials like Orichalcum, Gammanium, and Stardust Sand, sometimes requiring the blood of the Cloth's owner for critical repairs. His first major encounter unfolded when Libra Dohko dispatched Dragon Shiryu to Jamir. Mu tested Shiryu's resolve by demanding a blood sacrifice for cloth repair. Moved by Shiryu's willingness to sacrifice himself, Mu healed him and restored the Pegasus and Dragon Cloths. He later intervened to shield Shiryu and Dohko from Cancer Deathmask, disclosing his identity as a Gold Saint. During the Sanctuary arc, guarding the first Zodiac Temple, Mu defied the false Pope's commands. Instead of confronting the Bronze Saints, he repaired their Cloths and unveiled the concept of the Seventh Sense, the foundation of a Gold Saint's power. He later assisted Phoenix Ikki in retrieving Virgo Shaka from another dimension. In the Poseidon arc, Mu enforced Libra Dohko's directive for the Gold Saints to remain in Sanctuary, halting Leo Aiolia from directly aiding the Bronze Saints. He acknowledged the contributions of deceased Gold Saints like Sagittarius Aiolos and Aquarius Camus, whose Cloths autonomously supported the battle. The Hades Chapter marked profound trials for Mu. At the Aries Temple, he confronted his resurrected master, Shion, now seemingly allied with Hades and commanding the resurrected Deathmask and Aphrodite. Despite emotional anguish and Shion shattering his Crystal Wall defense, Mu refused to abandon Athena. He banished Deathmask and Aphrodite using his Starlight Extinction technique. Witnessing Shion in a Surplice deepened his distress, compounded by news of Taurus Aldebaran's death. Emotionally exhausted, he initially tried to send Pegasus Seiya away but relented, allowing him to stay and fight. Pursuing specters toward Athena, Mu defeated Papillon Myu in the Underworld by deciphering his fighting style, ensnaring him with the Crystal Net, and executing him decisively. He regrouped with Leo Aiolia and Scorpio Milo at Virgo Shaka's temple. Recognizing Shaka's sacrifice during his clash with three renegade Gold Saints—Saga, Camus, and Shura—Mu joined in unleashing the forbidden Athena Exclamation against them, fully accepting the consequences. At Hades' castle, he battled the Specter Rhadamanthys while severely weakened by a barrier Hades erected. Anticipating death, he fought to create an opening for the Bronze Saints before being defeated and cast into the Underworld. In the Inferno segment, Mu's role narrowed. Frozen solid, his primary act involved safeguarding Shaka's prayer beads and returning them upon Shaka's reappearance. His defining moment occurred at the Wailing Wall in the Underworld's depths. Alongside the surviving Gold Saints, he sacrificed his life force to breach the Wall, enabling the Bronze Saints to reach Elysium and rescue Athena from Hades. Mu possessed the strongest raw psychic power among the Gold Saints. His abilities encompassed telekinesis at a molecular level, telepathy across dimensions, teleportation, dimensional travel, illusion creation, and healing through blood flow control. Key techniques included Starlight Revolution, a devastating energy blast; Crystal Wall, a reflective defensive barrier; and Crystal Net, an entrapment method. He mastered the Seventh Sense and awakened the Eighth Sense, permitting him to enter and exit the Underworld alive. His character consistently balanced deep compassion and mentorship with unyielding resolve and lethal force when duty required, culminating in his ultimate sacrifice.