Icarr Ko, a Cathar of the male persuasion, existed in the era of the war against Zakuul. After the demise of Vaylin, the Empress of the Eternal Empire, and the subsequent establishment of the Eternal Alliance in the year 3630 BBY, he, along with his relative Nyris Ko, became affiliated with a clandestine group of Republic scientists led by Doctor Alirra Semhess. This group was conducting a covert operation aboard the X7-Cratus space station. Ultimately, Theron Shan, acting on behalf of the Eternal Alliance, uncovered Semhess's activities. Consequently, a strike force was sent to X7-Cratus with the objective of preventing RS-33 adrenal from posing a danger to the galaxy. Alliance forces clashed with and overcame Marlon Fenn. However, the confrontation resulted in damage to the station's containment infrastructure, leading to a RAK-5 serum leak into the atmosphere. Icarr and Nyris Ko confronted the invading forces while in an infected state, and tragically, they were both eliminated by the Alliance personnel after transforming into rakghouls during the battle.