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. In Kingdom Hearts II, after Roxas was integrated back into him, an awakened Sora and his friends resume their search for Riku and King Mickey, the latter's mentor Yen Sid re-familiarizing the trio with the Nobodies and Organization XIII's remaining members whom they deal alongside Maleficent and her right hand Pete. The three reunite with King Mickey and encounter Organization XIII's leader Xemnas, him and the Heartless Ansem revealed to the splintered halves of the real Ansem's apprentice Xehanort. The Organization's plan is also revealed: regaining their lost hearts by using Keyblade users to create an artificial Kingdom Hearts from slain Emblem Heartless. Axel, a rogue Organization member who is Roxas' friend and first encountered Sora in Castle Oblivion, abducts Kairi in an attempt to see Roxas. Axel's action only give Saix, his former friend and Xemnas' enforcer, leverage to force Sora into finishing what Roxas and Xion began. Axel sacrifices himself to help Sora's group reach The World That Never Was (Organization XIII's headquarters) and, after defeating Xemnas's right hand Xigbar, reunite with Riku and Kairi. DiZ, revealed to be the real Ansem, attempts dissipating some of the artificial Kingdom Hearts before being engulfed in an explosion when his extraction device self-destructs and is sent to the Realm of Darkness. Sora and his friends then battle Xemnas. After Sora and Riku defeat Xemnas, they get trapped in the Realm of