Known as Alpha-30 or A-30, Sull was an Advanced Recon Commando of the Alpha-class. During the Clone Wars, he held the rank of lieutenant within the Grand Army of the Republic.
Sull was dispatched to Gaftikar in 21 BBY. His task was to train the Marit people, who were marginalized on the planet, into a rebel force. This army was intended to overthrow the Human-favoring government of Gaftikar. During this operation, Sull vanished and was officially declared missing in action.
Omega Squad, accompanied by Sergeant A'den, were dispatched to Gaftikar two months after Sull's disappearance. Their objective was to assassinate key Gaftikari government officials, thereby facilitating a Marit coup. However, while reconnoitering the capital city of Eyat, Darman and [Atin](/article/atin_skirata], two members of Omega Squad, noticed Sull and followed him to an apartment within the city. After a brief scuffle, during which Sull bit Darman's hand, he was captured and returned to the Marit village serving as Omega's base of operations.
During interrogation by A'den, Sull made a startling revelation: Clones who attempted to desert the Grand Army were not executed for desertion itself, but because their trustworthiness was deemed compromised. He recounted the story of another clone, Tavo, a friend of his, who had tried to escape and was subsequently hunted down and killed by agents of Republic Intelligence. Sull's claims raised troubling questions about the fate of the GAR's clone troopers once the war concluded and their utility to the Republic diminished. While regular clones would almost certainly be retained due to their controlled independence and unwavering loyalty to the Republic, the future of the less-altered clones would eventually be viewed as more of a liability than an asset.
Ultimately, A'den chose to release Sull. Despite objections from Niner, he arranged for Sull to depart Gaftikar aboard Nyreen Vollen's ship and reported to the SO Brigade of the Republic that ARC trooper A-30 had perished from unknown causes during his mission. Soon after, Sull's statements were validated when two Covert Ops clone troopers attacked Darman, mistaking him for Sull.
Later in the conflict, Sull encountered Fi in a cantina on Mandalore. Surprised by this reunion, Fi was taken aback by Sull's condition. In the company of another rogue ARC trooper, Spar, Sull met former Jedi Bardan Jusik. Sull, enraged, demanded to know who had ordered the executions of Alpha ARCs who deserted, and he attacked Jusik. The former Jedi, understanding Sull's anger, attempted to pacify him. Fi, defending Jusik, reacted by punching Sull and threatening to kill him if he approached Jusik again.
Subsequently, Sull and Spar discovered that Kal Skirata was attempting to reverse the aging process and sought to join him. They agreed to assist in the liberation of Kal Skirata's Separatist daughter, Ruusaan Skirata, even though Sull still harbored animosity towards the Jedi and held a low, if not nonexistent, opinion of them.