Thrahk was an orc warchief who led the second invasion.
Not much is known about Thrahks early life except for that he was a grunt.
The second invasion
At sometime in his life the agents of Kol Thezar reached Thrahk. They possessed him and bent him to the will of the dread lord.
Under Kol Thezar's command Thrahk lauched the invasion of Belemondo and took the capital. There he was instructed to build a demon gate to bring the demon into the mortal realm from the twisting nether.
Upon entrance to Derear, Kol, forseeing no use for his pawn any longer, clove the head of Thrahk with his claw.