Native to a galaxy other than the Milky Way, the Drashigs are a species of vicious predatory beasts. They somewhat resemble huge elongated gastropods, and usually locate prey by scent. They are extreme omnivores, although showing a preference for flesh.
One famous story tells of a spaceship which crashed into the Drashig homeworld: by the time rescue arrived not only had the whole crew been devoured by the creatures, but most of the vessel itself as well, with only a few metal scrapes left behind.
Drashigs are enormous worm-like predators with a reptilian mouth filled with teeth. They also have three pairs or short eyestalks. They normally inhabit marshlands and seem to be able to move just as well on the surface, underground or underwater. They are strong enough to burst through a metallic hull.
Drashigs are social creatures, which live in groups of about twenty and, despite their large size, frequently hunt in trios. That they feel the need to hunt in groups likely indicates that they aren't the largest species in their native habitat.
- Doctor Who season 10 - Carnival of the Monsters (1972)