We Keyblade Masters have a special gift. We can extract a heart, be it our own or that of another. By continuing this cycle, it is possible to remain in the world of the living forever.
As a boy, I dreamed of seeing the farthest reaches of the World. If I only went far enough, there had to be a world out there in which no one had ever before set foot. And now I know of just such a world. If I become the first to open Kingdom Hearts' door, I can create a Next World in which light and darkness exist in perfect equilibrium.
So there I stood, with vast knowledge in one gnarled, dying hand, and newfound purpose in the other. The next step was clear: I needed a new vessel.
And that was when I met Ventus and made him my pupil. We were destined to meet, and I could sense the potential within him, but the boy was too benign for his own good. I came to the conclusion he was too frail to serve as a vessel, and decided to use him for a second purpose I had in mind.
I would remove the darkness from his heart and split him in two. Then I would have my heart of pure light, and my heart of pure darkness.