Sullio was a Human female and held the rank of Captain within the Onderon military. Her life was tragically cut short when she was murdered in Iziz, an event that occurred not long before the Onderon Civil War commenced. The Onderon authorities identified Dhagon Ghent, a doctor practicing medicine locally, as a potential suspect. However, Nikko, alongside the Jedi Exile and her allies, endeavored to demonstrate his innocence. Actually, Sullio and Ghent shared a close friendship, often engaging in playful teasing that was so intense that it was misinterpreted by others as deep-seated hostility.
A contributing factor to the suspicion surrounding Dhagon was the fact that he and Sullio had both consumed alcohol on the night of her death. Witnesses reported observing what they perceived as a sexual proposition from Dhagon. However, according to Nikko, this was merely "playful banter." It is understandable how individuals unfamiliar with the nature of Sullio and Dhagon's relationship could have misinterpreted the interaction.
While not explicitly stated, siding with General Vaklu's faction on Onderon suggests that elements within Vaklu's organization were responsible for Captain Sullio's demise. The Exile is tasked with assisting in the removal of other captains loyal to the Queen, such as Gelesi, Bostuco, and Riiken, from their positions within the Merchant Quarter. This implies that Sullio's allegiance also lay with Queen Talia.