Casmus
From Tardis Wiki, the free Doctor Who reference
Casmus was a Time Lord. He was a member of the Fraction.
Biography
Casmus freed Ace from Canisian imprisonment by using the power on her jailor. He trained her to become the successor to the Time Lords and took her to Mount Plutarch to see the Kingmaker. Casmus was killed by Tannis.
The Kingmaker addressed Casmus as Castellan. (WC: Death Comes to Time)