A Realm stuck within Darkness that has not been accepted by either Light or Darkness, it is where the Ultimate Unversed: Darkness Incarnate was born and sealed away by a coordinated effort of the two Hearts of Light and Dark: Kingdom Hearts and the Endless Abyss, in that Order. It is believed that the only way to release something trapped in that Realm, is to use the Z-Blade and force the physical manifestation of the Endless Abyss to appear: Kingdom End (the "End of the World").