Darbin Sull was a male Human from Corellia, distinguished as a promising political figure. He achieved the distinction of being among the youngest elected officials on the Corellian Council during the time of the Galactic War. Possessing immense ambition throughout the conflict, Darbin was secretly recruited by agents serving Imperial Intelligence when they approached him. They pledged to grant him the position of prime minister following the Imperial conquest. Subsequently, the Empire gained control over the entirety of the Corellian Council and deployed troops to the planet. To Darbin's astonishment, numerous Corellian factions and ordinary citizens mounted a strong resistance against the Sith Empire.
Darbin Sull had a mother whose face he professed to recognize. During his earlier years, Sull frequently engaged in jogging within Axial Park, and he had never discharged a blaster until the confrontation that took place at the park during the Battle of Corellia.
When the forces of the Jedi and the Galactic Republic became engaged in battle against the Sith and their Corellian allies, Sull made the choice to align himself with the Empire, motivated by his aspiration to be elected as prime minister.
Sull became a member of a hero team in a holographic discussion with Darth Decimus situated in Labor Valley. The hero had already successfully eliminated the surface resistance and destroyed their provisions, compelling them to retreat into the Selonian tunnels. Sull issued a warning, emphasizing the extreme ferocity of the Selonians and advising against underestimating them.
Following the Imperials' commencement of a genocidal campaign directed at the Selonians, the hero's attention shifted toward Axial Park. Sull was assigned the role of the hero's "prisoner," with the intention of "escaping" and infiltrating the Republic. The hero also opted to inflict a minor bruise on Sull to enhance the credibility of the deception. Unfortunately for Sull, the Republic harbored suspicions of him being an Imperial spy. To gain their favor, he divulged information about the Imperials' plot to assassinate Jedi Master Corin Tok. He succeeded in alerting the hero before the ambush, but he received a reprimand for the oversight.
The final territory slated for capture by the Empire was Capitol Square within Coronet City, where the Green Jedi constituted the last remaining resistance, having fortified themselves within the Green Jedi Enclave. Sull managed to obtain one access code for the hero's entry, but he was unable to secure another without compromising his cover. He informed his allies that all but one Green Jedi had sought refuge in the enclave, with the exception of Master Bedoch, who was endeavoring to defend the Republic Foundation Museum. The hero plundered the museum, eliminated Bedoch, and acquired his access code.
With all the necessary elements in place to eliminate the Green Jedi, Sull employed his charm to gain entry into the enclave, intending to divert the attention of the Green Jedi Council. As the hero infiltrated the premises, Sull volunteered to distract the Jedi, even at the cost of exposing his true allegiance, a proposal that received approval from his allies. Following the elimination of all the Green Jedi, the hero and Darbin Sull reported their triumph to Darth Decimus. Sull sought to remind the Dark Councilor of their prior understanding regarding the prime minister's position. Decimus conceded that he could envision Corellia undergoing reconstruction under Sull's guidance; however, he expressed concern that such a scenario would only incite renewed rebellion. Concurring with the Sith Lord, the Imperial hero resolved to eliminate Sull, striking him down just as his aspirations were on the verge of realization.
The player has the option to decide whether Sull lives or dies. If he is spared, Sull will be present during Corellia's induction into the Empire, where he will be honored with the title of Prime Minister. He subsequently implores his fellow council members to pay respect to the hero. However, Councilor Jalta pointedly refuses. Angered, Sull demands that the hero kill Jalta. The player can choose to kill Jalta (a dark side choice) or let him live (a light side choice).
If a Bounty Hunter chooses to spare Sull prior to the conclusion of the Corellia Imperial storyline, he will make an appearance in the Bounty Hunter storyline. Conversely, if Sull is killed, Prime Minister Cal Falcone will deliver his address and subsequently be executed by Darth Tormen.