The Watchers that fell or rebelled
dabbled in the DNA and the MIXING of the blood


The fallen Watchers took the original creation and sought to enhance it further-to use HUmanity and to 'take' the HUman women, and to combine seed

Thereby corrupting the original bloodline with the fallen Watchers who had left their first habitation

The mixing of said blood...allows the fallen to attach easier to those born of earth and of water...