Dark Forces

The Dark Forces originated at a time when humans were more in touch with their psyche. Because of this, they were able to perform psychic control. Using psychic control, they possessed a human doctor called Banham and used him to animate clay into walking "corpses" that were unleashed in England. The Eighth Doctor managed to dissipate the Dark Forces, thus relinquishing their control over the corpses. (EDA: Casualties of War)