From the writings of Guillermo Ramírez de Luna, first king of Los Nefilim:
In my first-born life, my name was Solomon, and I was the third king of all Israel. Of my father David’s many children, I was the only one born with the fire of the angels in my soul.
My father told me of the beginning days of the world, and now I leave my words for my daughter, who will one day rule Los Nefilim in my place.
During the first generations of the world, the daimons ruled the earth. They were the old gods, worshiped in the earth and water, and drew their sustenance from the mortals’ emotions--the stronger the emotion, the more powerful the daimon. The daimons often coupled with the mortals to create Nephilim, hybrid creatures neither truly spirit nor truly mortal. These Nephilim were the sorcerers, the prophets, the dreamers of the ancient times.
The angels came from sky; a different species made of fire and air. Their explorations of the numinous realms led them to the earthly realm, and once here, they fell in love with the mortals.
The daimons saw the angels as usurpers and refused to be subjugated. The most powerful daimons were those that fed on hate--Moloch and Ashmedai--and they led the others against the angels. The two groups warred and the skies shook with the thunder of their battles. They moved the continents and sank Atlantis beneath their fury. Both sides were equal in cunning and strength, so the conflict dragged on for years to become a stalemate between the powerful entities.
To break the impasse, the angels gambled that the daimons wouldn’t allow the mortals to be annihilated. They manipulated the realms and caused the deluge, and the rains submerged the earth. Millions of mortals perished.
When the daimons saw their sustenance dying, they capitulated to the angels’ demands and negotiated a treaty, but at no point during those mediations did the daimons mention their bastard children, the Nephilim. Unlike their parents, the daimon-born Nephilim weren’t restricted to the many covenants between the daimons and the angels. They set about the lands to provoke war and discontent in order to feed their parents’ insatiable appetite for blood.
When the angels discovered the daimons' children, they created a breeding plan of their own and set it into motion. Angels mated with mortals. Our race, the angel-born Nephilim, was produced to circumvent the threat of the daimon-born. With the Nephilim, the angels and the daimons could avoid another open conflict--their bastard children would decide future wars. Each side sought to breed the most powerful army.
Even today, the war goes on and the breeding programs continue ...