The Aries Gold Cloth is the Cloth of the Saint Mu in Saint Seiya, Soul Of Gold (where it becomes a god cloth), and Saint Seiya: Episode G, Shion in Saint Seiya: The Lost Canvas and Saint Seiya: Next Dimension, and Kiki in Saint Seiya: Omega. It is of the highest class of the Cloths that Athena’s Saints wield, the Gold Cloths.
The Aries constellation was based on the golden ram who rescued Phrixos and was sacrificed to Zeus to make the legendary Golden Fleece, which Jason and the Argonauts would pursue.
Mu trained to be a Saint in Jamir years before the birth of the modern Athena by the previous wielder of the Aries Gold Cloth, Shion. The Cloth was likely kept in Sanctuary until a Saint worthy of wearing it was found. Both Mu and Shion before him were capable of repairing Cloths. This doesn’t seem to be a specific trait of the Cloth so much as passed on training. Mu proved to be a valuable ally to the Bronzes, having fixed their Cloths, and helped defend Sanctuary from the invading Specters. Mu was trapped in Hell along with Aiolia and Miro, but awakened by Athena’s Cosmo, and rejoined the Gold Saints, to add his power to theirs, at the cost of his life. Shion died by the betrayal of Saga, who killed him on Star Hill, and took his place.
In Saint Seiya: Episode G, Aries Mu had already left Sanctuary to work in Jamir as the repairer of Cloths. Like Libra Dohko, he knew there was a corruption in Sanctuary, and stayed away because of it. When Leo Aiolia came to Mu to get his Cloth repaired, Mu initially refused, but was convinced by Aiolia to help him out and fight with him.
Lost Canvas/Next Dimension: Previous War
The Saints of Aries and Libra, Shion and Dohko, traveled together in Next Dimension, attempting to stop Hades from being reborn in the world, but failed due to Pegasus Tenma stopping them. Their newly received Gold Cloths weren’t enough, though, as the barrier weakened them as the Judges appeared. Shion learned via the Crateris Cloth that he is destined to be the future Master of Sanctuary. He eventually had to face his old friend Suikyo as a Specter, and was overpowered, being saved by the appearance of Ikki. In The Lost Canvas, Shion primarily serves as the one who repairs the Cloths. His big fight came against Balron Rune, who had tempted him to abandon the Cloths, and share in the power of the book he used to judge men. Shion defeated Rune, leaving himself as one of the few surviving Saints as the Holy War approaches its end. It is known that he survives both The Lost Canvas and Next Dimension, becoming the next Pope.
Saint Seiya Omega sees Kiki, the former apprentice of Mu, become the Gold Saint of Aries. At his first appearance, he is simply having his assistant Raki gather Stardust Sand to repair Cloths. Later on, he appears at the newly rebuilt Sanctuary, wearing his Gold Cloth, and seemingly gathering to Mars’ side. When the Bronze Saints began to assault the new Sanctuary, Kikiwaited for them in the House of the Aries. He warned them of Mars’ plan, and repaired their Cloths, draining his Cosmo in the process. He sent them along, preparing to fight the army of Martians that sought to take him out for betraying Mars. After Mars’ fall, he remains as a Gold Saint, as the new threat of Pallas arrives.