Kellman

Kellman was a civilian scientist sent to Nerva Beacon to act as an observer. He was paid in gold by a Vogan faction led by Vorus to ally himself with a group of Cybermen and bring them to Voga so they could be destroyed by the Sky Striker. He obeyed the Cybermen's instructions to use the Cybermats to infect the Beacon's crew with a plague, which killed off everybody except Commander Stevenson and Lester. He was later killed in a rock slide on Voga. (DW: Revenge of the Cybermen)