demoniac

nouns

someone who acts as if possessed by a demon
demoniac
is a type of (narrower)
a cruel wicked and inhuman person
demon, devil, fiend, monster, ogre

adjectives

frenzied as if possessed by a demon
"the soldier was completely amuck"; "berserk with grief"; "a berserk worker smashing windows"
amok, amuck, berserk, demoniac, demoniacal, possessed