A Pale Horse - The ARC Series, #1

Mythology is True. Magic is Real. And every nightmare you ever imagined walks the earth. The Watchers were tasked with protecting humankind. Instead, they lusted after them; lusted after their beauty, their creativity, their innocence. Some even took human women as their mates, but the children produced from this unholy union were unnatural, corrupt, wicked beyond redemption. They were The Nephilim.
And there was war in heaven: Michael and his angels fought against the dragon and his angels, and they were cast out into the earth. Woe to the inhabiters of the earth and of the sea, for they have come down with great wrath, and make war with the remnant of the holy seed.