infernal

Of or relating to hell, or the world of the dead; hellish.

He proffered a pact to Satan, calling upon the Fiend and working himself into a frenzy - but his infernal majesty failed to respond.

Of or relating to a fire or inferno.

Stygian, gloomy.

Diabolical or fiendish.

Th' infernal Serpent; he it was, whose guile Stird up with Envy and Revenge, deceiv'd The Mother of Mankind

the instruments or abettors in such infernal dealings

Very annoying; damned.

As I had to put up with the patronage and the lecturings, and the eyeglass of that infernal old woman, […]

When are you ever going to learn to mind your own infernal business?

An inhabitant of the infernal regions, a demon.