Azmael

Azmael was a benevolent renegade Time Lord who emigrated from Gallifrey to the planet Jaconda, a planet of flightless bird people where he settled and ruled there benevolently until Mestor deposed him.

Biography
On Gallifrey, Azmael worked as Co-ordinator of the Matrix and the Doctor's teacher. (source?)

During the Doctor's fourth incarnation, the Doctor and Azmael had met up. Azmael had drunk so much that the Doctor had thrown into a pool to get him to sober up. Mestor, who commanded the Gastropods, then came to power and used a telepathic link with him 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 limited number of regenerations.

Recently regenerated himself, the the Doctor, Peri and Hugo Lang come to Jaconda by happenstance, the Doctor recognized 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 Azmaels body and the Doctor destroyed Mestor's real body. Azmael, with Mestor's spirit within him, then forced himself to die by inducing a last regeneration. This causes the death of both Azmael and Mestor. (DW: The Twin Dilemma)