From the introduction:
There are three realms of existence. The Bitter Realm, ordered,uncluttered, constant, and crystalline. The Realm of Filth, hungry, dynamic, ugly, and incomprehensible. In between these realms lies our world, the Hollow Realm. It alone is malleable and yet ordered. The Realm of Filth and the Bitter Realm are at war. We are the weapons they use. Our deaths are the tally they keep. All sickness, all death, all evil, is external to man, inflicted upon us by the forces of the Worm and the Snowflake. They hide their war from the world, bury it in mundanity. The few that have stumbled upon the war quickly regret it.