From the Introduction: Black Mass is the game of fleeing your community into the dark, finding what you're looking for, and coming back. Catherine and Lydia flee their township during the witch crisis in the 1690s. They confront their demons in the woods, trekking to their own black masses. Players share responsibility of Catherine and Lydia as fractions of their personalities called personas. [...] Black Mass is a game about discovery: through play we learn about Catherine and Lydia, informed by the in-play personas.