The Doctor has been fighting the Cybermen ever since the final days of his first incarnation. Originally introduced on 1966's "The Tenth Planet," the Cybermen are Doctor Who's ultimate sci-fi body horror monsters. Once human, the Cybermen upgraded themselves, replacing human flesh with cybernetics and removing all emotions to become uniform, unfeeling, calculating cyborgs, set upon converting all humanity into Cybermen.
Source：https://www.cbr.com/doctor-who-cybermen-multiple-origins/
