From publisher blurb:
Our reality is ruled by monstrous gods, invisible horrors that hunger to consume us. Some deluded bastards worship these gods, trading obeisance for power or magic or the privilege of getting eaten last when the world ends. Cults are like cockroaches, breeding in the shadows, gnawing at the walls of society, fearful of the light… and bloody hard to kill.
This supplement for the Laundry Files roleplaying game delves into the murky realm of the cultist and the conspirator, detailing eight of the nastiest, most tenacious foes of the Laundry and dozens of minor ones.