What's is it about the undead that so morbidly fascinates us? This fascination ranges from the "Eww, a zombie!" to "Mmm, a zombie." Well, however much fascination you have for these rotting flesh-bags, you'll be happy to know that they have a place in the Whoniverse. As it turns out, the cause of these reanimations is a race of beings called Gelth, whose bodies were supposedly destroyed in the Time War. As a result of this, they slipped through the rift into 1860s Cardiff and taken up residence in the gas pipes. They are able to populate the bodies of dead humans and use them as 'vehicles.' Yummy.
