demoniac vs possessed

demoniac is a noun but possessed is not a noun.

Word	Noun	Adjective	Verb	Adverb
demoniac	Yes	Yes	No	No
possessed	No	Yes	No	No

As adjectives, demoniac and possessed are synonyms defined as:

demoniac and possessed: of, pertaining to, or like a demon or possession by a demon

Other synonyms of demoniac include demoniacal.

demoniac (noun)	possessed (noun)
someone who acts as if possessed by a demon

demoniac (adjective)	possessed (adjective)
of, pertaining to, or like a demon or possession by a demon	of, pertaining to, or like a demon or possession by a demon
	influenced or controlled by a powerful force such as a strong emotion