Xehanort

Master Xehanort (マスター・ゼアノート, Masutā Zeanōto), an old Keyblade Master from Destiny Islands who mysteriously disappeared, with Terra, Aqua, and Ven sent on a quest to find him. Furthermore, as his actions relate to the Princesses of Heart, Master Xehanort attempts to have Terra succumb to the darkness. In the end, Master Xehanort uses his Keyblade to transfer his heart into Terra's body there by corrupting Terra's mind, creating the current incarnation of Xehanort while he fades into darkness. However, the unforeseen creation of the Lingering Sentiment results in a battle which culminates in Xehanort's defeat before he could achieve his goal. Xehanort ends up in Radiant Garden after his battle with Lingering Sentiment and faces against Aqua who tries to reach Terra. After a long battle, Aqua defeats Xehanort who is dragged into the darkness by the Guardian Heartless, but Aqua, desperate to save Terra's body, casts her armor to send him to the Radiant Garden, where he is found by Ansem the Wise, Braig and Dilan. This incident leaves Xehanort amnesia, including that of wielding the Keyblade. Xehanort then becomes a student under Ansem.