Hell Magus

"You Will Die. ancient demonic curse*" The Hell Magus just before he fights the Doom Slayer.

Data
"The Hell Magus is the most powerful demon in Hell. It can blast fire and resurrect dead demons."

"We discovered that Hell Magi are the offspring of a Baron Of Hell and an Arch-Vile."

"A Hell Magus broke out of containment and killed all of the scientists. All we know is that it is-- screams*"

History
A Hell Magus, called the Devourer was to become King Of Hell before being slain by the Doom Slayer.

Glory Kills
On Itself: The Doom Slayer tears off one of the Magus' horns and impales it in in its throat.

On The Doom Slayer: The Hell Magus grabs the Doom Slayer by the throat and lifts him up. The Magus then combusts his arm and immolates the Doom Slayer.

Trivia

 * The Hell Magus had a scrapped animation where it summoned a Fire Imp.
 * It originated when John Romero was creating enemies and he wanted to make new enemies that were different than all of them. So he made a copy of a Arch-Vile and put the Baron's horns on the side of its head. The ID Software team was confused, so John gave them what the Magus comes from.