Sullio was a female Human and Captain of the Onderon military who was murdered in Iziz shortly before the start of the Onderon Civil War. Dhagon Ghent, a local medical doctor, was singled out as a suspect by the Onderon authorities, but Nikko and the Jedi Exile, along with her companions worked to prove his innocence. In fact, Ghent and Sullio were the best of friends and often engaged in teasing so extreme that other sentients mistakenly took it for intense animosity.
One of the reasons Dhagon was suspected was because he and Sullio had been drunk that night and witnesses saw what they believed to be a sexual advance by Dhagon. In reality, it was simply "playful banter," as described by Nikko, but it was easy to see how certain patrons who knew nothing about Sullio and Dhagon's relationship could have mistaken it for what it was.
Though it is never confirmed, if the player chooses to support General Vaklu's forces while on Onderon, then the story implicates subversive elements within Vaklu's camp for the murder of Captain Sullio, as the Exile is asked to help "remove" other loyalist captains from their posts around the Merchant Quarter, including Gelesi, Bostuco and Riiken. This presumes in turn that Sullio was loyal to Queen Talia as well.
Though it is never confirmed, if the player chooses to support General Vaklu's forces while on Onderon, then the story implicates subversive elements within Vaklu's camp for the murder of Captain Sullio, as the Exile is asked to help "remove" other loyalist captains from their posts around the Merchant Quarter, including Gelesi, Bostuco and Riiken. This presumes in turn that Sullio was loyal to Queen Talia as well.