The Cultists of Cathulhu have gathered: their Great Eldritch Ritual nears its end. There is just one thing left: choose one of them to Ascend and finish the ritual. It’s a simple choice, really. They are all the same — any of them will do! There is just one problem: some Investigators have infiltrated the ritual, pretending to be Cultists. And choosing any of them would ruin it all!

Cult of Cathulhu is a fast-paced hidden role game for 4-11 players. Engage as a Cultist, trying to find trustworthy brethren with your unique skills and solve the lie-filled riddle -- or as an Investigator, trying to sneak you or your comrades in to halt the Cultists’ world-ending plans.
Each player has two hidden cards: their alignment (Cultist or Investigator), and a separate skill card. Investigators are in the minority but know each other, while Cultists have to use their otherworldly skills in a search for just one Cultist they all can trust.

The game consists of three phases: Mission briefing, Council, and Voting.
Mission briefing lets the Investigators know each other, as well as other Investigators' skills.
In Council, players can freely discuss and use their skills. Most skills either give information, e.g., by seeing others' cards, or help other players use their more powerful skills.
Investigators can use their skills just like Cultists to fool them, with an extra advantage: they can use skills from any card, not just their own. Skill cards are always discarded after use, face-down. The Council is timed; after the time runs out, Voting begins.

In Voting, all players simultaneously vote for another player. All players with the most votes are chosen to Ascend, and the game ends. If all chosen were Cultists, the ritual succeeds and all Cultists win; if any of them was an Investigator, the Investigators win, instead.