The Four Game Masters

Ridley Sheldon
Count Ridley Sheldon (リドリー・シェルダン伯爵, Ridorī Sherudan Hakushaku), from London in the United Kingdom, is the first game master. Count Sheldon has a collection of dolls that he admires a lot. Sheldon's favorite doll, Fiona 「フィオナ」, has a blonde doll dressed up in a Victorian Outfit. Count Sheldon disguises one of his dolls as the school nurse. Sheldon defeats Yugi in a Duel Monsters game, taking his Neon Knight as a reward. Later, Seto kidnaps Yugi, whom is in the arcade looking for a new game called "KIS", so Yugi could face Count Sheldon again. Dark Yugi defeats Sheldon and placing a Shadow Game on the loser. Fiona's face is cracked after the duel with Yugi is over.



Yujīn Krabs
Yujīn Krabs (ユジンー・クラブズ Yujīn Kurabuzu) is the second game master, who has good luck with a television game show. Yujin pushes around Yugi and his friends until Yugi challenges him to a Shadow Game involving a game show. He ends up losing. After losing, Yujīn no longer has good luck on the TV game show and loses his champion title. Later, during the final Death-T episode, Aileen Rao and Ryuichi are paired against Miho and Jonouchi. Jonouchi and Ailean have the battle suits while Miho and Ryuichi are at the controls. Jonouchi and Miho defeat Aileen and Yujīn.

Aileen Rao
Aileen Rao (アイリーン・ラオ, Airīn Rao) is a Canadian-Indian dancer and who also happens to be the third game master. Kaiba tells Aileen, who returns from a Paris fashion show, to play a game against Yugi. Aileen first challenges a soccer player named "Heida" (平田) to a game of Rijinhai, a fictional version of chess from India. Aileen states that if he wins, she will submit to his will, but if Aileen wins, Heida will lose the most important thing to him. Aileen wins and Heida is seen injured in a hospital on TV. Aileen lures Yugi and Anzu, who is a big fan of Aileen, to her condominium. Aileen holds Anzu hostage and forces Yugi to play Rijinhai. Aileen tells the same thing to Yugi: if he loses, he will lose the most important thing to him. Aileen threatens to kill Anzu with a tiger if Yugi loses. Yugi wins and Aileen lets go of Anzu. Aileen acknowledges Yugi as a good player. Later, during the final Death-T episode, Aileen and Yujīn Krabs are paired against Miho and Jonouchi. Jonouchi and Aileen have the battle suits while Miho and Fuha are at the controls. Jonouchi and Miho defeat Aileen and Yujīn.

Daimon
Kaiba's butler, known as Daimon 「大門」 in the first series anime, Hobson in the second series anime and simply "Kaiba's butler" in the manga and the English version of the Dungeon Dice Monsters video game, is a sadistic man who engages in a shadow game with Yugi and his friends. He requires a life-support capsule to stay alive. He is able to leave the capsule for short periods, however. He and Seto were good friends when Seto was a child, with Seto bringing him snacks like oranges when Daimon first got sick.

In the manga, he manages a trap at Death-T. Yugi, Jonouchi, Honda, Anzu, and the butler have to sit in electric chairs while watching a scary projection. Anyone who screams is electrocuted. The butler knows how to not scream while Yugi and his friends are close to screaming. Johji wriggles free from Anzu's lap and defecates on the butler's lap. The butler screams and is electrocuted, freeing Yugi and his friends from the chairs. The butler dies after the electrocution.

In the first series anime Daimon is one of Kaiba's game masters. Seto releases him from the capsule so he can be the fourth opponent to challenge Yugi. By staging an accident, Seto is able to lure Yugi to duel Daimon. If Yugi refuses, Anzu will be devoured by a mechanical dragon. Seto provides Daimon with a device that will allow him to see Yugi's hand, but Daimon refuses to use it. After being defeated, Daimon takes Yugi aside and tells him to restore Seto's lost innocence.

He appears in the first episode of the second series anime to kidnap Sugoroku Mutou. He also appears during various flashbacks of Seto Kaiba's past.

In both the manga and 2nd series anime, he is the reincarnation of Gebelk.

Deck Daimon plays a Zombie Master Deck, focusing on getting his weak monsters destroyed and then bringing them back en masse with his "Zombie Master" card.