Deedrix headed the Savants in their arguments with the Deons, a religious order. The Deons forbade them from entering the power room where the Dodecahedron was kept. This angered Deedrix and the Savants who did not believe in the Deon god.
When the Deons staged a revolution, Deedrix was taken prisoner. However, a Gaztak attack meant that the Deons were needed to defend and so he was released. He helped save the Fourth Doctor moments before he was sacrificed.