Odion Ishtar, known as Rishid Ishtar in the Japanese and Manga versions, is the adopted older brother of Marik Ishtar and the second in command of his rare Rare Hunters in Yu-Gi-Oh!
Odion was adopted by Marik's parents, and was going to be the tombkeeper, until Marik was born (after his sister Ishizu). When Marik and Ishizu snuck out, their father punished Odion, but Yami Marik awakened inside Marik and killed his father. Odion contained Yami Marik within Marik.
He became one of Marik's Rare Hunters when Marik began seeking out Egyptian God Cards. During the finals of Battle City, Marik instructed Odion to pretend that he was Marik so that no one would know Marik's true identity. Odion dueled Joey with a deck of trap cards, and nearly defeated him, but Marik told him to finish Joey with the Winged Dragon of Ra. He summoned the fake Ra that Marik had given him, but the real Ra was angry for using a counterfeit Ra card and struck them both with lightning, knocking them out. Joey got up first and won the duel by default. Without Odion, Yami Marik reawakened.
Odion did not wake up until Yami Marik's duel with Yami Yugi, and attempted to help Marik defeat Yami Marik. In the end, Marik and Yami Marik were switched around, and Yami Marik was destroyed by Marik when he forfeited the duel.
Odion later appeared alongside Marik and Ishizu to witness the duel between Yugi and Yami, which was being played so that Yami could go through the door and rest.
Though he works for Marik as one of his Rare Hunters, Odion is not truly evil, and wants Marik's good side to overcome his evil side.
Yu-gi-oh! The Falsebound Kingdom
Odion appears as a recurring boss in Yu-gi-oh! The Falsebound Kingdom. You fight him once in both Yugi and Kaiba's campaign and three times in Joey's campaign. In all his appearances, he uses the same three monsters: Mystical Beast Serket and two Embodiment of Apophis, like in the anime.
In Yugi and Kaiba's campaign, you fight him on the level "Hallowed Land of Ishtar". When the player defeats Scott Irvine at Sygh-Varths, Scott flees to Ishtar in the deep southern region. After Marik Ishtar went into exile in Joey's campaign, Odion returns to his homeland to protect the temple in honor of his master. It is believed that Odion was unaware of Scott being inside the temple and that Yugi or Kaiba were there to desecrate it. Still, he sends four soldiers, each with spirit monsters and then the player can fight him. Once he is defeated, the player finds the secret room which leads them to the next level in the heart of the computer.
In Joey's campaign, a prequel, Odion has a bigger role along with Marik and becomes a rival to Joey Wheeler, like in the anime. Before the events of Scott, Emperor Haysheen was still in command and appointed Marik as high mage of the Imperial Order and sent him to take out Joey and his Black Dragon Squad. Marik sent Odion and several soldiers to the Chelyumn region. Once the player defeats the soldiers sent to your castle, the player can fight Odion and end the level. There is a bit of dialogue between Joey and Odion. Odion still wishes to take down Joey but becomes touched by Joey's courageous words and behaves more honroably towards him. In the next level, "Minion of Darkness", Marik and Ishizu Ishtar join Odion along with more powerful soldiers and fight Joey in the Beasty Badlands. Marik sends his entire army including Ishizu and Odion to Joey's party and after a certain amount of time, Mai Valentine appears and takes out the soldiers, leaving only the Ishtar family, making them retreat if Marik loses.
Odion appears one final time in the level "Master Plan" with Ishizu in the Nonnber region. Odion says Marik went rogue to find the power of the Egyptian Gods. Joey and his party must defeat Ishizu, Odion and ALL the soldiers to win the level. After winning the first time, Mystical Beast Serket joins the list of monsters. Joey then fights Yami Marik in the next level, Ishizu likely went to find Kaiba and Odion likely returned to the homeland, waiting for Marik's return.