DOOM (video game) - Cacodemon’s Song (Id Software)

Cacodemons are red monsters with large spherical bodies crowned with horns, that float slowly through the air. They have a single green eye over a large mouth which is persistently twisted into an evil grin showing a series of nasty teeth and a bluish interior. In Doom II, their instruction manual description says: They float in the air, belch ball-lightning, and boast one Hell of a big mouth. You're toast if you get too close to these monstrosities. They attack by spitting a ball of lightning or by biting with their gaping maw. The cacodemon often seems to distance itself from the player when under attack, though the cause of this is that it is being pushed back by successful hits from its enemies.
Cacodemons hiss when they first see the player or otherwise become active, and use the pain sound shared by most of the demonic monsters from Doom. When killed, they let out a gurgling moan and fall to the ground, splitting open like a burst pustule, spewing copious amounts of blue goo that flows forth, to reveal their bared brains while their sole eye pops out of its socket.
The name cacodemon, which comes from the Greek κακοδαίμων (kakodaimon) usually meaning "evil spirit", a more precise name for what we generally know as demon (which ultimately comes from "god" or "spirit"), is in English a word that may be found in most comprehensive dictionaries.