The Bible talks about the fallen angels looking upon the daughters of men and deciding to make wives of them. Hence the Nephilim, which are the Giants of Old, the men of renown. The Nephilim are the offspring between the daughters of men and the fallen angels. Genesis 6 goes into much detail about what happened between the mixing of the angelic and human seed. The Book of Enoch also acts as a companion guide to this story and explains the detail about how angels and demons operate in the lives of men and women on earth. Once the children of the fallen angels and women (Nephilim) died their spirits could not return to their heavenly habitation but were forced to make their abode in the aether in between heaven and Earth. This is also where we get evil and tormenting spirits from because they wonder to and fro seeking rest and finding none. The only please that these disembodied spirits receive is when they have a human host. A willing vessel that they can influence to do their bidding even if in subtle ways. The Book of Enoch tells us that they are able to feel again when they have a host. They are also able to taste meats and wines and have the pleasure of causing their human much strife in their life.
The new testament also goes into much detail about these demonic and unclean spirits. About 90% of Jesus’s ministry was dealing with the foul entities and leading people back to a state of true freedom and influenced by the fallen spirits. In the book of Matthew Jesus also lets us know what happens to the spirits once they leave a persons aura and lets us know how to stay free from future oppressions.