Watchers
The Watchers are an order of two hundred spiritual beings, formerly angels, who rebelled against Yahweh, descended to earth, taught forbidden knowledge, and engaged in sexual intercourse with humans. The hybrid descendants of the Watchers and human women are known as nephilim.
Great Descent
The Great Descent is the Satano-Grigorist name for the incarnation and descent of the Watchers to earth. It may also be applied to the time period during which the Watchers were incarnate in the physical realm; for example, one might refer to events that happened "during the Great Descent."