Valis was a villain whose goal was to have "dominion over all things". He was a disembodied being composed of gas-suspended carbon particles and was highly flammable.
Two weeks later, Valis joined forces with several aliens to try to kill the Doctor, their common enemy. He was shot by Zargath, who believed him the Doctor in disguise, and exploded in the face of his murderer. (COMIC: Death to the Doctor!)