From the introduction:
The Coven is a role-playing game about some outside, Other force that is trying to enter and destroy the world through its interactions with occultists who, against their better judgment, interact and bargain with the Other for their own benefit. In the game, one player will take on the role of an outside Other force, be that the forces of hell, an alien incursion, Mythos gods, etc. as they attempt to enter and destroy the town that the coven have unwittingly invited them into. The rest of the players will make up members of the Coven, people who on the surface are normal townsfolk, but all of whom have a secret desire for power that gets them into trouble.