Castellan Casmus was a Time Lord, or God of the Fourth, in a state of reality where the Time Lords had been all but wiped out during the Seventh Doctor's lifetime, with the surviving renegades having sworn to adhere by a strict code after what happened on Micen Island.
Having warned the Council of the Santine Republic about an impending invasion by General Tannis, Ace was captured trying to flee the planet. Casmus freed her from Canisian imprisonment by using the Power of Creation on her jailor. He trained her to become the successor to the Time Lords, setting her a number of trials, and took her to Mount Plutarch to see the Kingmaker. His companion was a cat named Midas. Casmus was later killed by Tannis while Ace undertook a test on the geo-psychic world of Anima Persis, Casmus having given her his TARDIS (WC: Death Comes to Time [+]Colin Meek, BBCi animations (BBCi, 2001-2002).)
