The Millennium Ring in fan-fics.
Yu-Gi-Oh! X - The Millennium Ring was recharged by the soul of the curator who defiled Pharaoh Seto's tomb and released an ancient evil. Shadi then tested Darin's worth to bare it by having an illusion of Gloria, his mother, appear and play a dangerous game with Darin. The Millennium Ring would be used as a die. Wherever the pyramid point of the Ring pointed, the person who didn't throw the ring would have to walk two spaces in that direction. Darin refused to participate in the game as he didn't want to risk killing his mother, and when he was about to fall into the pit, the illusion of Gloria disappeared, and Darin gained the Millennium Ring. The restored bond between Darin and Gloria also shocked Shadi into restoring the minds of Anzu, Serena, and Kira. Darin also uses the Millennium Ring to break Shadi's spell on Bakura. Around the time of Tag and Anzu's seventeenth birthday, Darin hears a laugh from the Ring. When he hears the laughter again, he wonders if he's going crazy, but Yami Bakura then uses his own bond with the Ring to takeover Darin. Yami Bakura then uses the Ring to take Tag to the Shadow Realm for a Shadow Duel. Tag wins, but Yami Bakura simply takes Darin's soul as a conselation prize. Darin then defeats Bakura in the Shadow Realm, and this severs Bakura's connection with the Ring. Mahad and Mana then decide to help Darin on his destiny to help Tag save the world. Shortly after this, Darin uses the Millennium Ring to replace his soul with Mahad's, and Serena's soul with Mana's to give them a day off. Darin then used the Millennium Ring's ability to hone in on Millennium Items to escape Death-T3 by having the Ring hone in on the Puzzle and the Rod. Darin later used the Millennium Ring to put Mana's soul in Serena again, so she could go on a date with the Pharaoh. During the date, Mana reveals that the Millennium Ring chose her after the incident with Zorc. Also, when Darin defeated Prisoner 777 in a Shadow Game, he used the Ring to burn away the prisoner's evil self in what he called, Flaming Soul. Also, the Ring is revealed to be able to hone in on former bearers as it reacted to Mahad and Mana during Duel Monster Spirit Day when they were Dark Magician and Dark Magician Girl. Darin then uses the Millennium Ring to have Mahad's mother, Anru, inhabit Tea's body while her soul was in Pegasus' possession to ensure her baby's survival as she was pregnant at the time. The Millennium Ring also reacts to when Bakura arrives, secretly being controlled by Yami Bakura. The Ring then has Mahad and Mana inhabit Darin and Serena's bodies again when Yami Bakura seals everyone's souls in their favorite cards. Darin also uses the Millennium Ring to allow all of his friends to see Mana, so she could lead them to where Bonz and his friends were forcing Darin into a duel.
The Little Dark Magician Girl - After Mahad was made into a permenant human, he gained the Millennium Ring and was made a member of Atem's court.
The Little Dark Magician Girl II: Return to the Ka World - Mahad still bears the Millennium Ring.
The Egypt King - Seven years after the death of Aknamkanon, the Millennium Ring chose Mahad over Bakura. Mana then gained the Ring when Mahad fused his soul with his Ka to make the Dark Magician.