Qetesh

The Qetesh were a species which fed off excitement in people's lives, draining their life essence with it. They were masters of emotional manipulation and were also known as "soul-stealers". (SJA: Goodbye, Sarah Jane Smith)

Biology
The Qetesh outwardly resembled humans, though they possessed far greater strength. Their stomachs existed outside their bodies. They did not need air to breathe. (SJA: Goodbye, Sarah Jane Smith)

History
The Qetesh imprisoned a member their species, who took on the name Ruby White. They placed the prison craft into space; Ruby escaped. She travelled to many planets and drained them. She was recaptured by Sarah Jane Smith. (SJA: Goodbye, Sarah Jane Smith)