Castle Oblivion

Castle Oblivion is an In-Between Realm world which appeared in Kingdom Hearts: Chain of Memories, and is the only real world in the game. It was previously controlled by Marluxia of Organization XIII, and consists of thirteen floors and twelve basements.

Each hall is completely white save for the doors at each end of it. Behind those doors is either nothing or....

The history of Castle Oblivion before Chain of Memories is still unclear, but it is known that it was eventually found by Xemnas of Organization XIII, who decided to convert it into a new headquarters for the Organization. It was intended to be a place to research memories, an important topic to the Nobodies of the Organization, who have only their memories to form personalities with. Xemnas sent Xigbar and Xaldin to recruit more members for the Organization, as they needed a large group in order to run the castle. Eventually, a strange Nobody named Naminé appeared in the castle and was found by the Organization. She soon became the center of their research, due to her strange abilities of memory manipulation. In order to further research, Xemnas also developed pods that could be used to piece together memories. The castle and Naminé were then entrusted to the neophyte Marluxia, but he would soon plot to use this power in a bid to seize control over the Organization. While Marluxia, and his associates Larxene and Axel controlled the top half of the castle, the senior members Vexen, Lexaeus, and Zexion controlled the basements.

Original Canon Story:
In Kingdom Hearts: Chain of Memories :

After defeating Ansem and restoring the damaged worlds, Sora, Donald Duck, and Goofy find themselves in a grassy field with the King's dog, Pluto. They follow Pluto along the path to Castle Oblivion, and as soon as they enter the castle, they forget all of their skills and are forced to rely upon the castle's memory-based card system. Though Marluxia and the other Organization members tell them their memory loss is simply the nature of the castle, it is revealed that the mysterious girl Naminé is actually the one reshaping Sora's memories, so that Marluxia and Larxene can use him as a puppet warrior against Xemnas. The scheme fails thanks to the meddling of Axel, and Marluxia and Larxene are lost to the darkness at Sora's hand. Sora then uses one of Xemnas' pods so that Naminé can restore his memories, and is eventually moved to Twilight Town.

Meanwhile, Sora's friend Riku awakens from the darkness within the lowest basement of Castle Oblivion, where he faces his memories of Maleficent and the remaining darkness of Ansem. Though he initially sets out to destroy the indelible darkness in his heart, with the help of DiZ, Naminé, and King Mickey, he is able to eventually embrace both the light and the dark, achieving balance. The three basement members, Vexen, Lexaeus, and Zexion seek to recruit Riku in order to counter Marluxia's use of Sora, but Riku denies their requests and vanquishes them. Riku eventually defeats the Ansem in his heart, and decides not to have Naminé seal it away completely by erasing his memories; instead he sets out on the "road to dawn" in order to help while Sora is sleeping.

In Kingdom Hearts 358/2 Days :

After members of Organization XIII are sent to Castle Oblivion (which starts the events in ), Roxas learns from Demyx and Xigbar that the members assigned to Castle Oblivion were annihilated. Xion later goes to Castle Oblivion seeking answers about her existence. Axel tries to stop her, but his efforts are futile. Later, when Roxas learns from Axel that Xion was born in Castle Oblivion, he becomes determined to investigate the place for himself. However, barely has he walked in the door when he is overcome by a strange weakness and passes out entirely.