Mentalis

Mentalis was a war computer.

Mentalis was built by Drax at the behest of the Shadow to direct the war between Atrios and Zeos. It was discovered by the Doctor while on Zeos with Shapp, Merak, Romana and K9. With K9's help they were all given the opportunity to see it and speak with it. They discover what it is and what it has been doing yet it refused to answer any inquires about Astra, nor will it allow them access to its databanks. With the war over, it decides it will destroy everything and everyone on both sides. The Doctor decides that the computer must be dismantled, then detecting the Marshal's attack ship it starts a self-destruct countdown and to prevent the Doctor from interfering with the countdown, it destroys its own control center.

Mentalis was an extremely powerful and nearly indestructible computer that could defend itself as well as produce and direct war material. (DW: The Armageddon Factor)