Toberman

Toberman was Kaftan's servant. He accompanied her on Professor Parry's expedition to Telos. He was captured by the Cybermen, partially cyberconverted, and placed under their control. When the Cyber-Controller killed Kaftan, Toberman regained his humanity and attacked the Controller. He sacrificed his life to close the electrified doors of the Cybermen's tombs, sealing them in. (DW: The Tomb of the Cybermen)