Casmus was a Time Lord and a member of the Fraction.
This article needs to be cleaned up to incorporate information from WC:Death Comes to Time in the main body rather than the "Behind the Scenes" section, as per "rule 4 by proxy" as agreed upon in Tardis:Temporary forums/Archive/An update to T:VS
These problems might be so great that the article's factual accuracy has been compromised. Talk about it here or check the revision history or Manual of Style for more information.
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.
The Kingmaker addressed Casmus as Castellan. Casmus introduced himself as "a God of the Fourth". (WC: Death Comes to Time)