Vahss served in the Republic Navy's starfighter corps during the Republic Dark Age alongside Captain Jenn Devaad. He was part of an ill fated Republic task force dispatched to Daalang which was captured and enslaved by the Hutt crime lord Zodoh after the local inhabitants refused to shelter them. For the next five years, he and his comrades served as slaves to Zodoh until they managed to escape. This small group of survivors became known as Devil Squadron and would fly Fire Lotus-class starfighters for Baron Lemayne's Grace Command, a mercy organization devoted to providing relief assistance to Sith-occupied worlds. However, Grace Command was in reality a front for Lemayne's black operations including Operation Deluge which involved inundating entire populations in Sith territory with the addictive spice Deluge as a means of undermining the Sith war effort. By 1032 BBY, Operation Deluge had succeeded in weakening the Sith's manpower resources at the cost of adversely affecting many civilian populations.
Vahss participated during the assault on Capital Cay when Devil Squadron "liberated" Aquilaris from Daiman and Zodoh's forces. Later, he was present at the spaceport when Jenn and the Jedi Knight Kerra Holt were distributing food and medical relief supplies to the civilian population. He was critical of his superior officer Jenn's decision to give Kerra Holt a place within their starfighter squadron, commenting that things could get tricky with a Jedi present. Jenn dismissed his concerns and assured him that Kerra would be too preoccupied with her mission to notice anything suspicious about Grace Command. She added that Kerra would be an important asset in the fight against their nemesis Zodoh, who was trying to make inroads into the Grumani sector. Vahss also expressed his desire to get payback from Zodoh for his wrongs.
Finally, Jenn commented that Kerra would never need to know about Operation Deluge if everything went right. However, Kerra's childhood friend Joad Kreel was eavesdropping on their secret conversation and learnt about Operation Deluge. The following day, Devil Squadron escorted the medical transport Mother Grace to a hyperspace jump-point in the Aquilaris Minor system. They then departed on a mission to fight Lord Malakite's forces on Heptooine. En route, they intercepted Zodoh's Intruder-class starfighter which led them into a trap. In the ensuing dogfight, Devil Squadron was trapped between Zodoh's flagship Voracious and a fleet of Stormdrivers, capital ships capable of generating artificial floods and storms.
Following a confrontation between Jenn and Kerra over the intercom, Jenn ordered Vahss to deactivate Kerra's Fire Lotus starfighter Devil Seven and bring her back in line. However, before he could comply, his starfighter was shot down by one of Zodoh's Infiltrator starfighters. Vahss died in the subsequent explosion. His death spared him captivity, torture and execution at the hands of Zodoh which marked the fate of his fellow comrades with the exception of Jenn.
John Jackson Miller had originally named Vahss as "Voss" before changing it due to the name being identical to one of his readers on Facebook.