Yrssk was a Trandoshan of the male persuasion. He served the Galactic Republic as an intelligence agent. In the waning years of the Republic, a middle-aged Yrssk, along with his colleague Klieri, received orders to travel to the planet Nyriaan. Their mission: investigate the Deluge Experiment, a clandestine climate-altering initiative spearheaded by the Corporate Sector Authority. Once on Nyriaan, Yrssk turned his back on the Republic, aligning himself with the CSA. He kept up appearances of loyalty to the Republic, all while fostering alliances with various native factions, including the Nyriaanan Malvina clan and a group of mutant Sith known as the Children of the Tempest. The CSA later assassinated Klieri, prompting Yrssk to sever all ties with the Republic. A team of Republic operatives then journeyed to Nyriaan to locate the missing agents. Yrssk attempted to trick the Malvina clan into eliminating the Republic agents by falsely portraying them as miners intending to establish a mine on their territory. However, his scheme failed, and the agents survived. Subsequently, Yrssk, alongside the Children of the Tempest, launched an assault on the agents in the Steamfields, a geothermally active zone on Nyriaan, where he met his defeat.