Marlon Fenn, a Mandalorian mercenary of the male persuasion, existed in the era of the war against Zakuul. After the demise of the Eternal Empire's Empress Vaylin and the subsequent establishment of the Eternal Alliance in the year 3630 BBY, he enlisted with Doctor Alirra Semhess's band of renegade Republic scientists. This group was involved in a clandestine endeavor aboard the X7-Cratus space station. Theron Shan, leading operatives of the Eternal Alliance, ultimately uncovered Semhess and her covert project. Consequently, an assault squad was sent to X7-Cratus with the mission of preventing RS-33 adrenal from escalating into a galaxy-wide menace. While attempting to stop the Alliance forces, Marlon Fenn was defeated in combat, but the battle resulted in damage to the station's containment protocols, leading to a RAK-5 serum breach into the station's air.