XIII機関
Organization XIII, a group of powerful Nobodies—the "empty shells" left over when a strong-hearted person becomes a Heartless—introduced in "", is established as the primary group of antagonists early on. Xemnas, the leader of Organization XIII, serves as the main antagonist and final boss of the game. Villains unique to the worlds are still prevalent, and are often presented as challenges that Sora's group must overcome.