Mü du Bélier, the Gold Saint of Aries, guards the first temple in Athena's Sanctuary. Born in Tibet, he trained under the previous Aries Saint and Pope, Shion, at the Sanctuary. He mastered psychic abilities to an exceptional degree, surpassing other Gold Saints in raw telekinetic power, enabling techniques like teleportation, psychokinesis, and advanced barriers. His skills extended to the specialized craft of cloth repair, requiring rare materials like Gammanium, Orichalcum, and Star Dust Sand. Restoration of severely damaged cloths required a blood sacrifice equivalent to one-third of the supplicant's blood volume. Following suspicions about Shion's assassination, he withdrew from Sanctuary affairs and relocated to the remote Jamir plateau. There, he lived in seclusion with his apprentice Kiki, focusing solely on cloth maintenance and refusing Sanctuary involvement unless approached directly. His initial encounters with the Bronze Saints occurred when Dragon Shiryu sought repairs after battles. He tested Shiryu's resolve before restoring the Dragon and Pegasus Cloths, establishing a pattern of aiding Athena's warriors despite his formal distance. Later, during the Bronze Saints' assault on the Twelve Temples, he guarded the House of Aries. Instead of combat, he repaired their damaged cloths and revealed the existence of the Seventh Sense, the foundational cosmo power utilized by Gold Saints. He remained behind with Kiki to protect Athena's unconscious body during the Sanctuary's climactic battles. The Hades conflict thrust him into a central and conflicted role. When deceased Gold Saints, including his mentor Shion, were resurrected by Hades to infiltrate Sanctuary, he faced profound loyalty conflicts. Shion, alongside Cancer Deathmask and Capricorn Shura, arrived at Aries temple demanding his allegiance to kill Athena. Torn by reverence for Shion, he initially hesitated to resist, even rebuffing Pegasus Seiya's attempts to intervene and teleporting the Bronze Saint away. This indecision proved costly, leading to his injury by the specter-possessed Gold Saints. Witnessing Taurus Aldebaran's death ultimately galvanized him to commit fully to Athena's defense. He later aided Leo Aiolia's swift counterattack. Throughout the Sanctuary arc of the Hades saga, he participated in critical defensive battles. He engaged the specter-general Wyvern Rhadamanthys alongside other Gold Saints, though the encounter occurred under conditions potentially suppressing their powers. His psychic techniques, including Crystal Wall and Starlight Extinction, were deployed against formidable opponents. He also played a crucial support role in Virgo Shaka's strategic sacrifice. Using his telekinetic abilities, he transported Shaka and the specter-possessed Gold Saints Saga, Camus, and Shura directly to Yomotsu Hirasaka, the entrance to the Underworld, facilitating Shaka's use of the Atavaka Exclamation technique aimed at Hades. He consistently displays a calm, analytical, and reserved demeanor, often perceived as scholarly or lordly, earning him respectful titles like "Lord Mu." He maintains deep respect for elders like Libra Dohko and shares a strong friendship with Taurus Aldebaran. His primary motivation stems from loyalty to Athena and a sense of duty, though his profound respect for his mentor Shion created significant internal conflict during the Hades invasion. This conflict defined his narrative arc within the Sanctuary chapter, transitioning from hesitation driven by past loyalties to decisive action in defense of Athena and the living world.