Father Modeenus was the high priest of the Imperial Rhumons. He pretended to be kind to Victoria Waterfield, but secretly modified the bomb in her shock collar. It was sent to activated when it detected Draga-three's voice. The Second Doctor realised this and defused the bomb.
He was brought under the influence of the Animus by the gold in his temple. He had become mentally unbalanced, which made the Animus reject him when it tried to absorb him. He went with the Second Doctor, Jamie McCrimmon, Kristas, Kai Shallvar and Draga-three to deliver a bomb to the Animus. The TARDIS materialised in a control chamber inside Vortis.
After the Animus was apparently defeated, Modeenus locked himself in the chamber. He piloted the planet towards the sun, intending to cleanse it of evil. A surviving Animus fragment attacked Modeenus, and the Doctor reluctantly activated a system that destroyed Modeenus and the fragment. (PROSE: Twilight of the Gods)