Realm of Light Edit
The most traversed Realm in the Planes of Existence is the Realm of Light. It is home to most of the stable worlds where Hearts and lives may be free. At the core of the Realm of Light is the Cornerstone of Light, a massive orb of pure Light that wards off Darkness and keeps the Realm protected. The King of the Realm of Light presides over the Cornerstone at his castle.
Near to the Cornerstone of Light is the Door to Darkness, a locked entryway straight to the deepest part of the Realm of Darkness from Radiant Garden. This door leads to the part of the Realm of Darkness where Kingdom Hearts resides.
Realm of Darkness Edit
Little is known about the Realm of Darkness, other than that is it the opposite of the Realm of Light, complete with its own set of inverted Keyblades. It is infested with Heartless of all kinds and sized, though mostly Pureblood Heartless, as they are attracted to large amounts of Darkness. Not surprisingly, there is very little light in this world, and even the sun on some worlds gives off less light than the full moon in the Realm of Light.
Somewhere deep within the Realm of Darkness is Kingdom Hearts, the light within the darkness.
Only four areas in the Realm of Darkness have ever been seen: The Dark Meridian, the area in front of Kingdom Hearts, the area that appears to be within Kingdom Hearts, and the Pure Darkness, where Corridors of Darkness lead.
Realm of In-Between Edit
The Realm of In-Between is a small space in between the other two Realms with no affiliation to either. This is the homeland of the Nobodies, and home to many strange places. Known worlds include Twilight Town, The World that Never Was, Castle Oblivion, and the Keyblade Graveyard.
Realm of Nothing Edit
The Realm of Nothing is a place outside existence where all things fade away. It is a universe comprised of truly nothing. No matter can survive here for long without dissipating into Nothingness. Only two places have ever been seen in the Realm of Nothing: Betwixt and Between, where Corridors of Darkness lead, and the empty area where Xemnas met his doom.