Nekghouls represented a more advanced and intelligent form of rakghouls. These creatures evolved within the ruins of Taris and had driven the Outcasts to extinction by the time the Cold War began. This was three centuries after the planet's destruction in 3956 BBY, a period during which they were, for a time, the planet's sole inhabitants. They were significantly larger and possessed greater intelligence than typical rakghouls, leading to the suggestion that they might be classified as a distinct species. Unlike the hunched posture of rakghouls, nekghouls stood upright, and they lacked the ability to infect or transform others.
The most significant difference between nekghouls and rakghouls was their sensitivity to the Force. However, they were untrained, and their aggressive reaction to intruders suggested a leaning towards the dark side. While capable of speech, their origins remained unknown, with no historical records to clarify their beginnings. One theory suggests they descended from the Outcasts. This led to speculation about whether they were Jedi or Sith who had been infected with the rakghoul plague, or perhaps the result of mutation caused from radiation by Taris' shattered reactors.
At one point, the Nekghouls came into possession of a holocron belonging to a Jedi named Bay-Yon Siu. For an undetermined duration, the holocron attempted to instruct the Nekghouls in the ways of the Force, hoping to help them achieve self-mastery, with limited success. Eventually, Jedi Knight Danah Jor sought to destroy both the holocron and the Nekghouls, believing them to be too dangerous to be allowed to live. A spacer aligned with the Republic was brought to the Nekghouls' territory, where they encountered the holocron and the imprisoned Danah Jor. The holocron and Danah Jor explained the Nekghouls' situation to the spacer, who then judged them based on their pleas and the information provided by both parties. After considering both sides, the individual allowed the holocron to continue teaching the Nekghouls in the ways of the Force and freed the Jedi Knight from his imprisonment.
Darth Gravus's attempts to sabotage the Galactic Republic's efforts to rebuild Taris revealed the work of Jedi Master Sulan to convert nekghouls to the light side of the Force.