Demon (n.) are the gods of a superseded civilization.
A Demon (n.) is not an 'earliest' thing: like gods, demons are creations of the human mind — made by something and out of something.
A Demon (n.) is not ultimate: get behind the demons and you find projections of the hostile feelings survivors harboured against the dead.
A Demon (n.) was evil before any spirit was good: the bad ones are older.
A Demon (n.) is a bad, repressed wish projected outward; the old belief only needs taking back into the mind.
A Demon (n.) is often a fallen god: when one people conquers another, the losers' gods become the winners' devils.