Interventionists: The Watchers (or Grigori), a group of angels, descended to Earth, taking human wives and teaching humans forbidden knowledge like metallurgy, weaponry, and sorcery.
The Grigori (from Greek egrḗgoroi, "The Watchers") are a group of fallen angels described in biblical apocrypha, who mated with women, giving rise to a race of hybrids known as the Nephilim—called giants in Book of Genesis 6:4.
References to Grigori appear in the Book of Enoch and Book of Jubilees.
The Book of Enoch states that there were two-hundred Grigori, but only their leaders are identified and named:
The Grigori are bound "in the valleys of the Earth" until Judgment Day (Jude 1:6)
Neighbor names on the same shelf include Watchers / Grigori (Enoch), seeders, princely blood, and older glosses such as Anna / Annak / Anasazi.