Dorf was a Krontep warrior and a former assistant of King Yrcanos who had been experimented upon by Crozier at the behest of the Mentors. In 2379, he attempted to attack the Sixth Doctor and Peri Brown, but they escaped.
Yrcanos and Peri later found Dorf and released him, but they were soon captured by Frax. They later escaped with the help of the Doctor, but Dorf was shot and killed by a passing guard. (TV: Mindwarp)