Samyaza was an angel who fell and married a human woman, Lilith (later Morgan). He fought over Noah's ark in Eye of the Oracle as a leader of the Watchers. Lilith drained some of his power in an attempt to get onto the ark, and he later brought it up in questioning her trustworthiness, but she convinced him that if she hadn't both of them would've been imprisoned, and then she would have been no use in freeing him. She later contrived his escape and he and his Watchers attacked the earth in Tears of a Dragon. Their children, a race of giants, were called the Nephilim.
The Book of EnochEdit
He is a fallen angel. He fell after Satan and the others, leaving heaven willingly rather being cast down, and leaving because of lust, not pride like the other demons. His 200 associates were called "Grigori" (Greek for "Watchers"). He and several other Grigori married human women and had giant offspring, called Nephilim. Their punishment is described: And the Lord said unto Michael: 'Go, bind Semjaza and his associates who have united themselves with women so as to have defiled themselves with them in all their uncleanness. And when their sons have slain one another, and they have seen the destruction of their beloved ones, bind them fast for seventy generations in the valleys of the earth, till the day of their judgement and of their consummation, till the judgement that is for ever and ever is consummated. In those days they shall be led off to the abyss of fire: and to the torment and the prison in which they shall be confined for ever. And whosoever shall be condemned and destroyed will from thenceforth be bound together with them to the end of all generations... (Enoch 10)
Samyaza's name means "infamous rebellion."