Zexion was a lab assistant of Ansem along with Aeleus, Even, Dilan, Braig, and Xehanort. When he and the other five lab assistants became Nobodies they formed Organization XIII.
He's one of the under ground members alongside Vexen and lexaeus and the trio tried to convert
Riku but that didn't work so Vexen made the replica
he took matters into his own hands after Vexen and
Lexaeus were Eliminated and when it turned out that the replica proved useless but his attempts were in vain when he was ultimately destroyed by Riku.
Powers and Abilities
Zexion's weapon of choice is the Lexicon and his power is Illusion. In Kingdom Hearts: Re: Chain of Memories, Zexion used his Lexicon to mimic Riku's weapon the Soul Eater and create copies of himself. In Kingdom Hearts II, he uses the power of Illusion to send Sora and his pals to a different dimension. Afterwards, Zexion will create copies of his Lexicon and then hide himself in one of them. Sora must find the Lexicon that has Zexion in it. Meanwhile, the other Lexicons will attack Sora, Donald, and Goofy by hitting them, creating explosions, or shooting energy. Zexion's most powerful move is where he takes Sora, Donald, and Goofy to a pitch black dimension with three lights. Zexion himself is in the blue light. Sora must make it to the blue light before the lights stop moving. Once they do, the area, except where the blue light is at, will be bombarded with meteors.
Zexion is a playable character in Kingdom Hearts 358/2 Days. You can use him in Mission Mode. His Lexicon remains his weapon of choice alongside other books. While he's fairly weak in terms of physical strength, he specializes in magic. He can use his Illusion ability to make his books do attacks such as making claws or teeth come. His special attack is where he bombards the field with Meteors.