Ansem the Wise is an original character created for the Kingdom Hearts series. He first appeared in the "Reverse/Rebirth" mode of Chain of Memories under the disguise of a mysterious man named DiZ and appeared again in Kingdom Hearts II. The name "DiZ" is an acronym for "Darkness in Zero". Ansem was formerly a respected sage and ruler of the Radiant Garden. As a researcher and ruler of his world, Ansem studied the heart and delved into the many secrets of the worlds. He and his apprentice, Xehanort, believed that darkness could spread into and take control of the heart. After meeting with King Mickey, Ansem ceased the experiments when he heard his research may be connected with a current crisis happening on other worlds. He later found his report on the experiments was given new entries by Xehanort, now using the name Ansem as his own. Ansem's apprentices then betrayed him and banished him to a world of nothingness, where he took on the name DiZ. From that point on, until he cleared his name and had his revenge, DiZ wore concealing red robes and covered most of his face with red bandages.
In Chain of Memories, he helps guide Riku through his encounters in Castle Oblivion. Soon after Riku joins in his campaign, DiZ convinces Naminé to move Sora, Donald, and Goofy to Twilight Town for safekeeping. However, learning that Naminé is having increasing difficulty in stabilizing Sora's memories, DiZ sends Riku to capture Roxas in hopes that the Nobody's reunion with Sora can complete the restoration. In Kingdom Hearts II, Naminé begins to act on her own and Riku declines to help him in his revenge. As he observes the lengths that Riku is willing to go to in order to help Sora, DiZ loses his lust for revenge and grows regretful of his actions. When Sora awakens and embarks on his new quest, he does not function as DiZ wants, and all of his plans fall apart. In the World That Never Was, he reveals himself to Mickey while attempting to digitally seal away Kingdom Hearts. However, the hearts prove unpredictable and begin to overload the machine, and Ansem chooses to sacrifice himself in order to help defeat the Organization. After apologizing to Roxas for his mistakes, the machine self-destructs, and Ansem is consumed in the blast which disrupts the power contained in Kingdom Hearts and restores Riku to his true form. However, as revealed in Kingdom Hearts Birth by Sleep, Ansem was not killed, but ends up in the Realm of Darkness, donning the Organization's cloak as he meets Aqua, telling her that Sora is the only one who save them now.