Valis

Valis was a highly flammable disembodied being composed of gas-suspended carbon particles. He was "high arbiter of the darkness" and wanted dominion over all things.

Biography
Valis captured the Eighth Doctor and Izzy Sinclair after having stolen the Crystal of Consciousness. However, the Doctor had swapped the crystal with a piece of perspex and Valis was defeated.

About a fortnight later, Valis travelled in a spaceship across a couple of parsecs to Research Base Truro, transmitting security protocols to bypass the quarantine. There, he joined forces with several aliens the Doctor had defeated before to try to kill the Doctor. 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!)

Behind the scenes
In an interview with Jonathan Morris released in The Widow's Curse the description for Valis was given as; "cowled in robes like the Ghost of Christmas Yet To Come. He should look scary and enigmatic".