- You may be looking for Signus A.
Signus was a magician who served Lord Waldean de Beauvain and aided him in usurping Geoffrey de Beauvain, placing him in a deep hypnotic trance. When the Third Doctor and Haval escaped, Signus pretended to help them by leading them to his quarters, then re-imprisoned them. Signus then convinced Waldean to let him try to cast a spell which would switch their bodies with Geoffrey's and the Doctor's. When the Doctor and Geoffrey successfully resisted the magician's attempt, which took the form of illusions, the spell backfired on them, and they fled from the terrifying visions over the castle wall to their deaths in the moat below. (COMIC: The Magician)