The great giants were the children of the Watchers, fallen angels who took for wives beautiful and comely daughters of earth men. As they grew these giants ate all the possessions of men (see Azazel). And when could no longer sustain them, these giants turned against them and devoured mankind. Then when finished they turned against, some version say copulated with, birds, and beasts, and reptiles, and fish; and then ate each other’s flesh, and drank each other’s blood; and finally they were killed. A.G.H.
Cavendish, Richard, The Black Arts, New York: Peigee Books, Berkley Publishing Group, 1967, pp. 285-286