The Heartless

Creatures born from the darkness within peoples hearts, they seek only to take more hearts from people, eventually seeking out the Heart of the world they are on and taking that as well, gathering Hearts until the doorway to the Heart of all Worlds, Kingdom Hearts, is opened and the Darkness within can run rampant across the worlds.

The only threat to the Heartless is the Keyblade Master. The Heartless have great fear of the Keyblade, for it can seal the door to Kingdom Hearts, and constantly seek out it's wielder, trying to take his heart. The heartless are able to track the wielder of the keyblade by the strength of his heart when he holds the keyblade. They are mindless (though somewhat intelligent) creatures, and are relentless in pursuing their goal, attacking in hordes and never letting up, ever vigilant in their pursuit of eternal darkness.