History
The first six members of Organization XIII are Nobodies of assistants of Ansem in his experiments in darkness. The assistants and Ansem built an underground facility in Hollow Bastion, where they conducted experiments with the heart, using themselves as test subjects. After speaking with the off-worlder, King Mickey, Ansem saw the immorality of what he was doing and ceased his involvement. The assistants and their leader, Xehanort, did not share his moral compunction and continued their experiments. This eventually led to tragedy and the creation of Nobody versions of the assistants. Xemnas, the Nobody of Xehanort, became the "Superior" and founded Organization XIII in order to learn about the secrets of the heart and to recover their hearts and become complete beings again. To that end, they deliberatly send Heartless into various worlds with the expectation of Sora killing them, releasing the hearts inside the creatures, which then bond with Kingdom Hearts, granting more usable power for the Organization to use.
Nobody
Nobodies are creatures without hearts. They are leftovers, existing as merely the body (an empty vessel) and soul of people who lost their hearts to Darkness. Unlike the Heartless, the Nobodies attack people out of confusion and the need to be complete (finding and reuniting their bodies with their lost hearts). The members of Organization XIII, being the most powerful Nobodies because of their strong hearts, kept human form while weaker ones assumed malformed, inhuman forms. Most of the members of the Organization tend to control one type of Nobody, usually suited to their fighting style.
There are twelve known types of natural Nobodies; those being Assassin, Beserker, Creeper, Dancer, Dragoon, Dusk, Gambler, Samurai, Sniper, Sorcerer, and Twilight Thorn. They continue to run wild in the World that never was.
