Castle Oblivion is one of the primary worlds of the Square Enix's video game series, Kingdom Hearts. Formely the Land of Departure, re-constructed and re-modeled by Aqua as the current world, Castle Oblivion appears as the main setting of Kingdom Hearts: Chain of Memories, where the three heroes Sora, Donald, and Goofy journey through the location to find their friends. It is formely ruled by the Organization XIII's members, Marluxia, Vexen, Axel, Larxene, and Lexaeus, before their elimination by Sora's friends. Xehanort's Heartless also appears in the castle, on purpose to taunt and humiliate Riku, while marking his way out of the fortress, before his defeat by the latter.
Regarding the villain tournaments context, Castle Oblivion appears as one of the central worlds of the CG realm. Particularly, in Disney vs. Non-Disney Villains canon, Castle Oblivion is formely featured as Xehanort's castle, and then as Pitch Black's new residence, after overtaking it from Xehanort himself. It also appears in the second Disney Villains War, formely as a base controlled by Marluxia, and then by Maleficent, before her battle with the Organization XIII's members.