Ansem (otherwise known as Xehanort), The Seeker of Darkness, is the main enemy of Kingdom Hearts and Riku’s side of the story on Kingdom Hearts: Chain Of Memories. Xehanort was originally the Keyblade master who succumbed to darkness and ended up fusing himself with Terra. He lost his memories and worked for Ansem the Wise. Him, along with Braig and the other apprentices, began experimenting with human hearts without permission, each of them (Except Braig) becoming a Heartless (their Nobodies founding Organization XIII) in turn. Xehanort then took on his master's name, and his Heartless became the "Seeker of Darkness".
 Before Kingdom Hearts Birth by Sleep
Ansem time traveled to Master Xehanort as a teenager to recruit twelve other vessels through time.
 Between Kingdom Hearts Birth by Sleep and Kingdom Hearts
 Kingdom Hearts
 Kingdom Hearts: Chain Of Memories
 Kingdom Hearts 3D: Chain Of Memories
 Journal Entries
 Kingdom Hearts
 First Entry
A researcher who studied the Heartless and delved into secrets of the worlds. He organized his findings into a single volume known as Ansem's report. When he inexplicably vanished, most of its pages were scattered to the winds.
 Second Entry
As a researcher and ruler of his world, he studied the Heartless and delved into the many secrets of the worlds. While studying the heart and the darkness within it, he was possessed by darkness and ultimately destroyed his own world. He sacrificed his body to attain great power, and later possessed Riku's to regain a physical presence. Failure to stop him means the end of all worlds.
 Kingdom Hearts: Chain of Memories
Pursuer of darkness. To open the door to darkness, Ansem used the Heartless to steal countless hearts. He enslaved Riku, but met his demise at Sora's hand. Nonetheless, Ansem's shadow lives on in the depths of Riku's heart.
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