Father Kenneth Sheridan was one of the fictional characters created by Jason after he was made Master of the Land of Fiction.
He wanted to kill Rosemary Chambers because he thought she was an evil witch. The Seventh Doctor made him see that she was not evil, and he repented of his actions. He was the last victim of Phil Chambers, providing the remaining energy for the Force to be freed from beneath Arandale Keep. (PROSE: Conundrum)