Zuulan Sentar was a Gran intergalactic slaver during the time of the Jedi Civil War.
Though Zuulan was a common criminal, he had high ambitions, not afraid of pursuing his trade even in the most closely guarded sectors of Republic space. He was always careful in his own mind, rarely straying far from his landspeeder in case he needed to make a quick escape. Among those implicated as his customers were the wealthy settlers of Dantooine, including Ahlan Matale. Whether Zuulan sold only slaves to these settlers or if he sold other illicit goods, and whether Matale was indeed among the purchasers, has not been determined. Regardless, it all took place under the nose of the Jedi Enclave there.
Zuulan remained obscure until he attempted to kidnap the daughter of a Coruscant senator. The girl was recovered, and Zuulan escaped with his life, but his delusions of grandeur had gained the attention of the GenoHaradan: a secret society of bounty hunters with a vested interest in preserving the Republic. The GenoHaradan feared Zuulan would attempt another high-level abduction, this time perhaps succeeding, after which he could ransom his hostage for valuable political secrets. Zuulan could then sell these secrets to enemies of the Republic, potentially turning the tide in a war or insurrection.
In an optional dark side quest of Star Wars: Knights of the Old Republic, Revan took the GenoHaradan assignment to have Zuulan killed on Dantooine. Zuulan's speeder, on which he relied to get out of tight situations, actually brought about his downfall. Revan either planted a frag mine on the speeder and watched Zuulan die in the explosion, or set off the speeder's alarm, confronting Zuulan and his battle droids when they came to investigate. If the latter occurred, Zuulan would have fought a brief skirmish before offering all his credits in exchange for survival. Considering Revan could have taken the credits anyway, and considering Zuulan was a dangerous slaver, it is unlikely Revan accepted this offer.
The player actually has an opportunity to offer Zuulan the chance to surrender and be taken alive, an offer Zuulan refuses. Even if this is done, the player receives Dark Side points when Zuulan is defeated. Ethically, it is strange that the player receives no Dark Side points for letting Zuulan, an unrepentant slaver, go free in exchange for credits.
Strangely, Zuulan is the only Gran that is given a name to appear in Knights of the Old Republic.
When Zuulan speaks, he sounds more like a Gamorrean than his own species.