Grathan was a male Human Sith Lord who served the Sith Empire during the Cold War before going rogue and turning against the Empire. Grathan declared himself the thirteenth Dark Council member, with his own power base and sphere of influence within the Sith hierarchy. Although his claim had not been widely recognized, he controlled a substantial private army on Dromund Kaas. The Dark Council authorized all-out warfare against Lord Grathan and anyone who supported him.
After being driven from the Citadel, Lord Grathan holed up in his estate outside Kaas City. His forces there were made up of apprentices, loyal Imperial troops and cybernetic supersoldiers he developed in his secret weapons labs. His cadre of elite Scientists—some volunteers, others kidnapped and forced into service manufacturing a seemingly endless number of War droids, as well, reducing attrition in Grathan's army to near zero. One of the his apprentice was Vereta Fraabaal. Grathan lost his son and wife to Darth Baras's apprentice.