One thing that really winds me up is a statement that you often hear from Neo-Pagan wishful thinkers: ‘The Christian demons are just the gods of pagan religions.’ I don’t like to speak in absolutes, but very, very often the demons of Christianity were the demons of whatever religion dominated before Christianity. There were times when Christians said other people’s gods were demons (lots of rather hot words were exchanged during the persecutions and counter-persecutions of the Roman Empire, but those were difficult times). Generally though, Christianity preferred to spread by adopting and adapting. That’s why we have Irish Gaelic deities as Saints, and Halloween on October 31st.
The historian Philip Almond describes 1550-1700 as ‘the golden age of the demoniac’. There are a lot of reasons, one of the biggest being the Reformation. Demoniacs had been important in the days of the early church, when church fathers were trying to build a new religion in an environment of borderline (and sometimes outright) hostility. On the other hand, as D P Walker tells us in his book Unclean Spirits, by the middle ages there were no more pervasive threats to subvert. Christianity was the ruling religion of Europe, and those heretics who did exist could be hunted directly by fire and the sword.