Zargath

Zargath was an alien whose Imperial Militia had been at the Powell Estate for only five minutes when the Ninth Doctor used his sonic screwdriver to make it rain. Zargath's people were allergic to water and were quickly defeated.

Some time later, Zargath joined forces with other aliens that had been defeated by the Doctor to try to kill him. He shot Valis, believing him to be the Doctor in disguise. Being a highly flammable gaseous alien, Valis exploded, blowing Zargath to smithereens. (COMIC: Death to the Doctor!)

Behind the scenes
Jonathan Morris' short story The Zargathon Menace for the charity anthology Perfect Timing, which is not considered valid by this site, features Zargath's species.