Hath

Appearance
Hath are fish like humanoids. They wear grey jumpsuits while in battle and brown boots, and they bear green devices to breath. They have purple growths on their heads.

History
Hath originated on the planet Messaline, they got into a war against the Humans on Messaline in the search for The Source.

Myths and rumours
It was rumoured Hath are red bubbles that communicate through expanding and letting out smaller bubbles. It was also rumoured one of them will kill Jenny at the end of the episode. Doctor Who Magazine 395 reveals that Hath do communicate through bubbles but are humanoid fish.