The scripture warns us about the Enemy in a number of places. He is like a roaring lion, seeking whom he may destroy. We wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. He is the Father of Lies. And if you resist him, he will flee.
But it also warns that even the casting out of demons may not be permanent. The scripture describes the formerly possessed person as a house that is clean and in order. But it appears to be open and unguarded against the former resident demon. And finding it so, the demon fetches seven of its buddies and returns to set up shop, leaving the possessed person worse off than before.
Dante’s Tempest: Part 2. Let the story begin.