The Nobodies are a type of creature originating from the Kingdom Hearts series. They are the left-over pieces of a person after their heart has been taken by the Heartless.
Nobodies remained widely unknown and unheard of in The World until the Heartless experiments performed by the apprentices of Ansem the Wise. After losing their hearts and becoming the Heartless Apprentices, the bodies and souls left behind became Nobodies. The technical first humanoid Nobody, Xemnas, gathered the Nobodies of the other apprentices and formed Organisation XIII, naming each one of them. After this, the Organisation took command of many of the smaller Nobodies, and continued to have command over them until their eventual defeat. After that, many Nobodies appear to have moved on independently.
Nobodies, unlike Heartless, are constructed of the body and soul of a person, not the heart or the heart's darkness. Normally, the pieces fade away into non-existence when a Heartless is created, but if the person possessed a powerful will, then the body and soul would be willed to move on their own.
While they can and are often created in the Realm of Light, they cannot be born there. If the body and soul are forming a Nobody, they are sent to a world in the realm between (a vague zone crossing the gap between the Realms of Light and Darkness) to be born.
In return for the ability to plan and form together as a group, Nobodies trade in the heart's ability to feel emotions. Although they can react based on memories of their former life as a complete self, they usually cannot experience true emotions. Special Nobodies, however, suffer from the opposite - while they can express real, baseless emotion, they do not possess memories of their former life and have to re-learn how to live. These extremely rare Nobodies usually exist due to their other selves still having selfhood and form in the Realm of Light, stopping them from collecting those memories, and the connections they hold to their former selves may influence their ability to emote.
Nobodies appear to be stronger than Heartless due to their ability to strategise, which Heartless cannot do. In the Battle of One-Thousand Heartless, the Nobodies are shown defeating various Heartless. Saïx also takes control of the Heartless from Maleficent, implying that the higher Nobodies are capable of leading the Heartless, and that they are able to control darkness. Humanoid Nobodies also possess the ability to create Dark Corridors, which allow them to traverse between worlds without a Gummi Ship. Unlike the Heartless, however, they are heavily implied to be in danger of being destroyed when surrounded by darkness, which is why the Organisation's uniform is a black coat known to have darkness-warding abilities.
Nobodies, unlike Heartless, are divided into a clear hierarchy and power structure. While the weakest Nobodies are the constantly mutating Creepers, the Dusk is often referenced as the lowest form of Nobody structurally, and are the equivalent of Shadow Heartless in terms of frequency. Both of them are considered extremely low-ranking, and are just about human in appearance, though much more flexible.
Common Nobodies that are not Dusks or Creepers are considered to rank highly. They are specialised, with more distinctive appearances. They also have less greys and more desaturated colours. The names of these Nobodies reflect Final Fantasy job titles, and they each have a commander in the Organisation.
The Organisation represent the most powerful kinds of Nobodies. They are entirely human in appearance, and usually sport the exact appearance of the person from whom they were created (Roxas and Naminé being special cases). These Nobodies each command a type of common Nobody, which appears to be a non-optional trait. Each of these Nobodies also possesses command over a particular magic element. As the Organisation Nobodies possess full personalities, intelligence and memories, they possess their own special hierarchy based on ability, date of creation, and usefulness, with Xemnas at the top.
Though Nobodies cannot naturally shift between these forms and ranks, it has been implied that a higher-ranking Nobody can be forcibly turned into a Dusk as punishment. As rebelling members of the Organisation have only been assassinated, the actual truth of the claim is unknown.
The remaining members of Organisation XIII are the antagonists of The Interference, appearing as they did in Kingdom Hearts II. As they did in the original game, they attempt to steer Sora into collecting hearts for their artificial Kingdom Hearts, while also having to deal with Alexander Karsath.
Of particular note from the Organisation is Axel, the Nobody of Lea, who is struggling with the decision to leave the Organisation and look for Roxas on his own. Though he originally died at the end of the game, Alex stops him from destroying himself and, later, he regains his heart.
Roxas is another member of the Organisation, having left before the beginning of the game. He is captured by DiZ and Riku at the beginning and merged with his other self, Sora. He is, however, brought back to the surface as a counterpart voice by Joumae after they engage in a battle with Sora and Alex.
Naminé is a special kind of Nobody created from Kairi's heart when Sora freed it from his body; as of such, Naminé does not possess either her original self's body or soul. Instead, Naminé is composed of very little. She has command over memories belonging and relating to Sora, which made her an asset to both the Organisation and to DiZ. Eventually, she recombined with Kairi as they escaped from the World that Never Was, and after a while became a counterpart voice.