"At last, I'm free at last... freed from this... this... accursed tomb... this... prison... finally, I can have my revenge..."
-Hitt'lon Zizz'lii upon his release from his prison
Kingdom Hearts also known as "The Prison" and "The Tomb" is the prison built to imprison Hitt'lon Zizz'lii by the Ancient Society of the Malica Universe, but, this did not stop him, however, as he tried to escape from it for over a centrillion years, manipulating events to try and free himself from it. From starting the Ancient Keyblade War to manipulate Master Xehanort. He finally escape from Kingdom Hearts by the unwilling help of a group of heroes.
Its' been said that Kingdom Hearts is the heart of all worlds within the Malica Universe, and in sense, it is, as it contains the last remnant of a society long gone, but this remnant is anything but benevolent, with it holding a cruel tyrant whom abuses led to his imprisonment so long ago, forever trapped in a shapeless, formless, white void, which has repeatedly driven him both insane and sane numerous times over the eons trapped inside of it. Perhaps that's why when Hitt'lon finally escaped from his prison, his psyche was so unstable and his actions during his war so violate and unpredictable.