Karsim was a soldier in the Republic Army during the Great Galactic War, a conflict between the Galactic Republic and the Sith Empire. Later, Karsim joined the Republic Special Forces Division's clandestine black ops program as part of an assassination squad called the Surgeons. However, the squad was imprisoned on the planet Berrun after they began targeting the families of their enemies.
During the Great Galactic War between the Galactic Republic and the Sith Empire, Karsim functioned as a soldier within the Republic Army. He was a member of a squad under the command of Sergeant Fideltin Rusk, a Chagrian. Their initial mission involved liberating numerous Republic prisoners of war from an Imperial outpost. However, the intelligence they received was flawed, leading the squad to face a larger enemy force than anticipated. Despite this disadvantage, the squad successfully rescued all the prisoners and escaped with serious injuries, but without any fatalities.
In the years that followed, Karsim, along with other members of his squad, was recruited into the Republic Special Forces Division's black ops program. Under the direction of General Elin Garza, the squad, which included fellow veterans Naja and Eckerd, was assigned to assassinate Imperial leaders. Soon, the squad, now known as the "Surgeons," began to target the families of their intended victims. As a result of these war crimes, Karsim and his comrades were arrested and given life sentences in a detention center on the planet Berrun.
Karsim began as a loyal soldier, but his time in the Special Forces black ops program transformed the trooper into a killer who disregarded the ethical principles of warfare. Sergeant Rusk was deeply troubled to discover that his former squad had crossed the line by targeting women and children. He was disappointed that Karsim and the others, whom he had once considered the finest soldiers under his command, had undergone such a drastic change.
Karsim's name was first mentioned by the Jedi Knight companion character Fideltin Rusk in the 2011 video game Star Wars: The Old Republic.