In the 2360s, he served as an slave overseer in the mining colony of Korvat, which was under the command of Gul Zarale. For much of Kozak's tenure, productivity in his section was insufficient to meet the requirements of the colony. This was in part attributable to the ruthless manner in which he undertook in duties, even when compared to other overseers. In response to his having orders thirty slaves to be put to death during a single two month period in 2361, at least a dozen of his slaves entered into a plot to assassinate him. A Terran slave named Keiko Ishikawa had her lover, the Cardassian overseer Glinn Broca, arrange for her to have a meeting with Zarale, at which she informed him of the plot to kill Kozak. After the relevant slaves were taken into custody, Keiko suggested to Zarale that he spare their lives as further deaths in Kozak's section would only result in increased inefficiency. Zarale followed her advice.
In reality, Keiko was an operative of Memory Omega who had manipulated Broca into arranging the meeting so that she could find her way into Zarale's bed. Over the course of the next four years, she gradually gained his trust and was able to subtly manipulate him, as she had done with her previous lover Broca. By 2365, Kozak had become a drunkard who was no longer able to perform his duty to the required degree. Given that he had been found derelict, he was relieved of his position and executed by two Cardassian guards at Zarale's orders. At the time, Kozak had been "breaking in" a newly arrived female Bolian slave in a hovel and was so drunk that he could only manage a few unintelligible grunts before being shot dead. Keiko succeeded him as overseer and served in that position until she and 98 other slaves escaped to Terok Nor, the headquarters of the Terran Rebellion, in 2375. (DS9 - Mirror Universe short story: "A Terrible Beauty")