Azmael

Azmael was a renegade Time Lord who emigrated from Gallifrey to the planet Jaconda where he ruled compassionately until Mestor deposed him.

Biography
On Gallifrey, Azmael worked as Coordinator of the Matrix and was the First Doctor's teacher. (PDA: Divided Loyalties)

At some point during the Doctor's fourth incarnation, the Doctor and Azmael had an encounter in which Azmael drank so much that the Doctor had to throw him into a pool to sober him.

When Mestor, who commanded the Gastropods, came to power on Jaconda, he used a telepathic link with Azmael to dominate his mind. Under the guise of Professor Edgeworth, the villainous Mestor forced Azmael to kidnap the two young genius identical twins, Romulus and Remus Sylvest. By this time, Azmael had reached the end of his regenerations.

Recently regenerated himself, the Sixth Doctor, along with Peri and Hugo Lang, came to Jaconda by happenstance. The Doctor recognised Azmael as a friend from their homeworld of Gallifrey. Cooperating with Mestor in order to save his people, Azmael abandoned the Doctor and Peri, resulting in them being taken captive. When Mestor took possession of Azmael's body and the Doctor destroyed Mestor's real body, Azmael, with Mestor's spirit within him, forced himself to die by inducing a last regeneration. This caused the death of both Azmael and Mestor. (DW: The Twin Dilemma)