Robot Yeti / The Great Intelligence

First appearing in The Abominable Snowmen (1967) the Robot Yeti resemble the Yeti that supposedly live in the Himalayas, their outer skin disguising a small spherical device that provides its motive power. They serve the Great Intelligence, a disembodied entity from another dimension. Initially the Yeti were a ruse to scare off curiosity seekers, later serving as an army for the Great Intelligence. they would appear in four stories of the classic era.

SEASON 5 (1967-68): The Abominable Snowmen	SEASON 5 (1967-68): The Web of Fear
Robot Yeti make brief appearances in The War Games (Season 6), when the Doctor gives evidence in his defence to the Time Lords, and there is one in the Dead Zone in The Five Doctors (1983). Neither are considered Robot Yeti stories. They returned, still working for the Great Intelligence, in the spin-off video film, Downtime (1995) which features some Doctor Who alumni.
Downtime (1995)