The Cybermen were originally human beings, but gradually they replaced their weak mortal flesh with metal and plastic. In the process they lost their compassion, along with all other emotions.

Originally from Mondas, Earth's twin planet, the Cybermen were thought to have died out in our universe. But when the Doctor visited a parallel world, he found they'd been created again there, by the insane genius John Lumic. These Cybermen sought to 'delete' all who stand in their way, and could electrocute with their touch.

The Cybermen voyaged across the Void to invade our Earth, in the past as well as the present, building apelike Cybershade creatures to serve them and launching their ultimate weapon, the giant Cyberking. The last time the Doctor encountered them en masse, he hurled them back into the Void. But can the Cybermen ever be truly defeated