From the introduction:
As the light of the Good Folk dawned on the world, the creatures of the night retreated to dark corners, unable to withstand the piercing gaze and strength of arms that opposed them. In this Age of Heaven, many great structures and accomplishments grew from their harmonious labors and enlightened thought. Such was the Citadel of Anoros, home, workshop, and cathedral to an angelic being from whom it draws its name.
But lights cannot burn forever. And darkness is always lurking, inevitable.