DOCTOR: The Voracious Craw.

MARTHA: I see.

DOCTOR: Ooooh, they’re a terrible lot. Each one is the size of a vast spaceship. They just go sailing about with their mouths hanging open, devouring things. Devouring everything they come across. They look just like, I dunno, gigantic inflated tapeworms or something. Only much worse. If your planet attracts a Voracious Craw into your orbit... well. I don’t hold out much hope. No sirree. They just go... GLLOOMMPP! And that’s the end of you. That’s the end of everything. They’re just so... voracious, you see.