Marsen held the rank of lieutenant, serving the Galactic Empire in the year 3 ABY. This male officer participated in the Battle of Hoth, functioning as a lieutenant within the Imperial ground battle group. Following Lord Starkiller's killing of Captain Keenah, Marsen was appointed as Starkiller's new point of contact for the remainder of the conflict. Marsen furnished Starkiller with technical information pertaining to Rebel technology during Starkiller's assignment.
Marsen held the rank of lieutenant within the ranks of the Galactic Empire during 3 ABY. In that year, when the Galactic Empire became aware of a Rebel presence on the planet Hoth, an Imperial fleet was dispatched to eradicate it. The Empire deployed Starkiller alongside the Imperial forces, being aware that Luke Skywalker, the young Rebel Jedi who was responsible for the destruction of the Death Star, was present with the Alliance. During the subsequent engagement, Marsen oversaw the ground assault by the Imperials on Echo Base. During this battle, Starkiller killed Captain Keenah, his personal liaison, and Marsen was chosen to step in as Keenah's replacement.
At one point during the mission, Starkiller came across a shield generator, which was preventing him from getting into the main base. Marsen reached out to Starkiller and explained how the shields could be deactivated.
Once Starkiller had bypassed the shield barriers, he made his way to the heart of Echo Base, where he swiftly dealt with the Rebels stationed there. Marsen then let Starkiller know that their forces had taken out the shield generator that was protecting the base and that their troops would be arriving shortly.
As Starkiller continued to eliminate Rebels, Marsen informed him that their commander, Luke Skywalker, was in the vicinity, and relayed to Starkiller that the Emperor desired Skywalker to be taken alive, if at all possible. After Starkiller arrived at another Rebel command center, troops from the 501st arrived to provide assistance; Marsen directed the Sith Lord to the main Rebel hangar, where Starkiller engaged Skywalker in combat, ultimately turning him to the dark side.
Marsen, who was a lieutenant within the Imperial Military, served with the Empire's ground troops during the Battle of Hoth. Following the unfortunate demise of Keenah, he was selected as Starkiller's replacement personal liaison, and he soon demonstrated his competence by displaying his understanding of mechanics and shield generators while assisting Starkiller.
The non-canon Hoth scenario in Star Wars: The Force Unleashed: Ultimate Sith Edition marked the debut of Lieutenant Marsen.