He was portrayed by the late Andreas Katsulas, who also played G'Kar in Babylon 5, the One Armed Man in The Fugitive, and the Romulan Tomalak in Star Trek: The Next Generation.
A member of the Kleezantsun, Koulak ran an alien version of Russian Roulette on the slave ship Gruza where he would force Tectonese to sit in front of a device with half a dozen nozzles. The nozzles would either shoot out hot steam, or a stream of salt water, which was deadly to Newcomers. He forced Ruthra - the brother of the slave who would later be known as George Francisco - to play the game. Ruthra died in the game. Koulak then forced Francisco to play. They were down to the last nozzle, which would surely have shot Francisco with salt water, however that was the same day that the Gruza crashed on Earth. There was no time to continue the game.
About five years after the Gruza crashed Koulak restarted the game on Earth, murdering Tectonese. Francisco told Matthew Sikes about how his brother died in the game, and how he had been forced to play prior to the Gruza crashing.
Francisco tracked down the game, and forced Koulak to play the game. However he had left the salt disconnected, so that when the last nozzle went off it only shot harmless plain water at Koulak. As Koulak was being placed under arrest, Francisco told him he wanted Koulak to remember all the victims of his game.