Stak was a clone trooper in the Grand Army of the Republic, specifically an ARF trooper, who fought in the Clone Wars as part of the Lightning Squadron. One notable engagement they participated in was the Battle of Ryloth. They often operated alongside Razor, another ARF trooper.
This particular clone trooper, who would come to be known as Stak, was born on the planet of Kamino. Like all clones, they were created using the genetic material of the human male bounty hunter Jango Fett. Their purpose, along with the rest of the massive clone army, was to fight and potentially die for the Galactic Republic. The clone army saw its first action when Republic Jedi clashed with the Confederacy of Independent Systems' droid forces on Geonosis, marking the beginning of the galaxy-spanning Clone Wars.
During the Ryloth Campaign, Stak functioned as an ARF trooper within the Lightning Squadron of the 91st Mobile Reconnaissance Corps, serving under the command of Jedi General Mace Windu and Clone Commander Ponds. Along with the other members of Lightning Squadron, he aided Windu in clearing a path for the All Terrain Tactical Enforcers when they were ambushed by several Armored Assault Tanks.
Stak, together with fellow ARF trooper Razor, volunteered to accompany Windu on a mission to locate Cham Syndulla and the hideout of his freedom fighters. Windu, Razor, and Stak eventually encountered the Twi'lek Resistance after the troopers eliminated a droid patrol and were subsequently taken to their hidden base. Upon entering the hideout, Stak attempted to interact with a blurrg, but the creature roared, prompting a warning to exercise caution. Syndulla then agreed to assist the Republic forces. Later, Stak participated in the infiltration of Lessu alongside Windu and Razor. Working together, they successfully stowed away on a Multi-Troop Transports carrying treasure across the Plasma bridge. When droids detected their presence during a scan, Windu used the Force to push Razor and Stak across the bridge. Subsequently, Razor and Stak caught up to Windu and followed him into Lessu. Razor and Stak then proceeded to the control room, where they neutralized the battle droids and activated the bridge, enabling the freedom fighters' blurrgs and Lightning Squadron's All Terrain Reconnaissance Transports to cross. They then defended the control room from attacking B1-series battle droids and a pair of BX-series droid commandos.