Organization XIII
In "Kingdom Hearts: Chain of Memories", Sora's search for Riku and Mickey leads his group to Castle Oblivion, a fortress controlled by a mysterious group of non-existent "Nobodies" called Organization XIII, the castle's overseer Marluxia using the power of a girl named Naminé to alter the group's memories for his agenda. After Marluxia's defeat, the three are placed in a year-long sleep by Naminé to restore their original memories while losing their experience in Castle Oblivion. At the same time Sora ventured through Castle Oblivion, Riku ended up in the basement levels and ascends to the ground floor with Mickey's aid while dealing with a Replica of himself that fought Sora. Finding the comatose Sora while joining forces with the mysterious DiZ, Riku helps Naminé keep his friend safe until he is awoken. In "Kingdom Hearts 358/2 Days", a snag in the plan over the year forces Riku to capture Roxas—Sora's Nobody and Organization XIII member that came into being when Sora briefly became a Heartless in the first game-after he was forced to defeat and absorb Xion, a Replica of Sora in Kairi's image.