Master Xehanort is the main villain of video game, Kingdom Hearts Birth by Sleep. He is the original incarnation of Xehanort.
Biography
He first appears with Ven as trying to use his darkness, but fails. As a result, he extracts the darkness in his heart, resulting in the creation of Vanitas, who will become his henchman.
Xehanort has Ven sent to train with Aqua and Terra. He has him pit against Vanitas to create the x-blade to create a Keyblade war, and manipulates Terra into giving into darkness.
After Terra defeats Master Eraqus, Xehanort kills his mentor and reveals his true intentions. He orders to have him, Aqua, and Ven meet him in the Keyblade Graveyard.
Xehanort fights Terra with Vanitas. During the battle, he has used his Keyblade to transfer his heart into Terra's body, resulting in the modern-day Xehanort. However, he is defeated by Aqua, and has amnesia as a result.