Doctor Who: The Armageddon Factor (TV)

The final segment of the Key is traced to the planet Atrios, engaged in a long war with the neighbouring Zeos. The Marshal of Atrios intends a final strike to destroy the Zeons, but the Doctor and Romana discover that Zeos is deserted and the war is being co-ordinated by a computer called Mentalis, built by one of the Doctor's old Time Lord Academy friends, Drax. The computer is under the control of the Shadow, an agent of the Black Guardian. He and his servants, the Mutes, are inhabiting an unseen third planet positioned between Atrios and Zeos.