Marko was a male Human who served as a lieutenant in the Thaereian military during the Clone Wars. In about 21 BBY, Marko was based aboard a Thaereian customs corvette in the Cularin system, where he was tasked with inspecting starships that were departing from the system. While en-route to the Ando system, Strike Force Cularin, a Galactic Republic flotilla, approached the customs vessel and Marko contacted the force, to order them to prepare to be boarded.