From the introduction: Cailleath is a city like no other. Shifting constantly between the world and Faerie, its inhabitants have aspects of the creatures of both. Nearly every being that lives in Cailleath possesses some form of arcane power, either from inclination or in selfdefense. The sudden shifts to Faerie can be hard on those who are not attuned to the flow of arcane energy, and so very few non-magical natives remain in the city for long.