Jestan

 was an ally of Mertil. He tried to kill the Fifth Doctor with a defibrillator. He murdered Hervey on Mertil's orders and attempted to frame the Doctor. He accompanied Mertil and the people in pursuit of the Doctor, Nyssa, Turlough and Seksa and attempted to use the defibrilator on the Takers' forcefield, an act which rebounded and killed him. (AUDIO: The Whispering Forest)