In Club of Cthulhu Card Game, 2–4 players assume the roles of daring researchers performing forbidden rituals to glimpse the secrets of ancient gods. Each turn, players “sacrifice” a manuscript into one of five arcane decks, invoking omens and triggering deity powers as they push their luck in a delicate balance between revelation and madness. 

Omens drawn from the ritual circle reveal which gods are stirring. Matching three or more signs of the same deity grants that god’s blessing—and unlocks powerful abilities. But each blessing also limits your endgame scoring, and drawing too much divine attention may lead to a complete mental collapse.

Players must decide when to stop and when to delve deeper, risking additional sacrifices to gain knowledge or activate devastating effects. Timing, bluffing, and strategic manipulation of the ritual decks are key to claiming victory.

The game ends when the ritual burns out (two decks are emptied), or when a player receives all five blessings—vanishing in madness. Only those who’ve best hidden their insights from the gods will score and survive.