Weevil

The Weevils are a humanoid alien race, who come through the Cardiff space-time rift from their (unknown) homeworld and live in the Cardiff sewers. Not much more is known about them, not even what they call themselves, except that they are vicious and don't communicate very well (which is why nobody knows what they call themselves).

Physiology
Weevils are roughly human in shape and size, but are a bit taller, and have odd faces with many sharp, fang-like teeth.

Due to their overall outward physical similarity with Humans, many Humans mistake them for other Humans at first, and when they see the face and teeth they assume the Weevil is a Human wearing a very realistic prosthetic mask, which one police porter likened to Hellraiser, shortly before being attacked by the Weevil at his neck, causing a thick spray of blood to go everywhere.

Behaviour
Weevils seem to be vicious, blook-sucking creatures (as seen when one attacks the police porter mentioned in the previous paragraph), and apparently do not communicate, or if they do, only with grunts and roars.


 * Captain Jack Harkness explained that the Weevils do not usually feed off blood, but in the sewers eat "you can guess what".

Source

 * TW: Everything Changes