Putting the Cybermen on ice.

After the Cybermen managed to annoy most of the known Universe, to the extent that they were almost completely wiped out, they decided to stay out of the limelight for a few centuries. Having invaded the Planet Telos, which became their main base following the destruction of Mondas, the Cybermen stole the deep freeze technology created by the planet’s native inhabitants, the Cryons.

They built tombs in which to hibernate until the heat wore off, and froze themselves until, in The Tomb of the Cybermen, a group known as the Brotherhood of Logicians decided to defrost them in the hope of forming an alliance. Not a very logical move, really.

Be careful how you defrost a Cyberman, as they have a tendency to go mad and hit things if it’s not done properly. Practice with fish fingers and work your way up.