Realm of Darkness

The Realm of Darkness (闇の世界, Yami no Sekai) is a realm made up of Darkness in people of every world. As with the Realm of Light, this realm has a Keyblade, Kingdom Key D, which Commander Arthoross had obtained. Kingdom of Hearts is found here within its deepest depths, though it can only be accessed when the Final Keyhole is unsealed. This is also the home of all the Heartless and where even the most powerful ones can be found.

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 * —About the Realm of Darkness.