Q: By the time Sora finds Castle Oblivion it is under the Organization’s control; however, they did not create the castle but merely stumbled upon it. So, what is the true origins of Castle Oblivion?
A: Castle Oblivion was originally the Land of Departure, a world situated on neutral ground, balanced between light and dark. Upon becoming a master, Aqua was instructed by Master Eraqus to keep the land safe. If anything were to befall him, she was to take his keyblade and seal the land away forever. Upon his death, Aqua returns to the Land of Departure and does just that, transforming it into Castle Oblivion, in order to have a safe place to keep Ventus while his heart slept. Due to its creation by Aqua’s hand, only she knows how to solve its many mysteries.