That's the reason for the flood in a nutshell. To destroy these hybrid beings and their offspring The nephs attempt to change their fate failed. These spirits can only possess human beings rather than mate with them. They are cast out by the Word of GOD.and/or fasting and prayer When Jesus sent the cast out demons to the swine the animals drowned themselves rather than allow these spirits to abide in them. Believers have eternal life, satan doesn't.