Aries Mu stands guard at the Sanctuary's first temple during the conflict with Hades. Originating from the Himalayan region of Jamir, he trained under the previous Pope and Aries Gold Saint, Shion. After Shion's assassination by Gemini Saga, Mu distrusted the corrupt Sanctuary leadership and retreated to Jamir. There, he dedicated himself to repairing damaged Cloths while upholding his duties as a Gold Saint. When Hades' forces invade the Sanctuary, Mu faces resurrected Gold Saints and invading Specters. Confronted by his former master Shion, now serving Hades in an Aries Surplice and ordering him to kill Athena within 12 hours, Mu refuses. This defiance sparks a battle where he defeats Cancer Deathmask and Pisces Aphrodite before engaging Shion directly. Witnessing tears on the faces of other resurrected Saints like Gemini Saga, Aquarius Camus, and Capricorn Shura during this conflict causes Mu significant emotional turmoil, suggesting their actions may not be true betrayal. Mu displays heightened combat prowess and tactical intelligence in these encounters. He analyzes the abilities of foes like Papillon Myu, developing the Crystal Net technique to counter him before securing victory with Stardust Revolution. He joins Leo Aiolia and Scorpio Milo in executing the forbidden Athena Exclamation to counter a similar attack by the resurrected Gold Saints. Later, he safeguards Virgo Shaka's prayer beads, facilitating their return during the expedition to the Underworld. Compared to earlier stories, Mu exhibits increased resolve and willingness for direct combat. Initially, he teleports Pegasus Seiya away from the Sanctuary battle to protect him, citing the Bronze Saints' prior sacrifices and deeming their further involvement unnecessary. However, he later relents upon recognizing Seiya's unwavering determination. Following the Sanctuary battle, Mu travels to the Underworld. He attains the Eighth Sense, enabling his soul to remain active after physical death. He joins the other Gold Saints in sacrificing their lives to destroy the Wailing Wall, allowing Athena and the Bronze Saints to advance against Hades. Beyond the Hades Chapter, Mu appears in spin-offs. *Episode G* depicts him collaborating with Taurus Aldebaran and Leo Aiolia against Titan forces, utilizing his teleportation abilities strategically. *The Lost Canvas* portrays his lineage, showing his predecessor Aries Shion as a survivor of the 18th-century Holy War, further contextualizing the Jamir heritage and Cloth repair traditions.