Don't Mess with Cthulhu is a social deduction game complete with secret identities. Players are either Investigators attempting to keep Cthulhu from waking and controlling the world, or Cultists that try to bring the world to a disturbing end.

The game plays over four rounds. The Investigators need to uncover all the Elder Signs to win; the Cultists win when Cthulhu is revealed or if the game ends before all the Elder Signs are found.

Before each round players gets a number of Investigation cards, which they look at before shuffling them and putting in front of themselves so they know what cards they have, but they don't know which card is which. Each round has a number of actions the same as the number of players in the game. Players take actions to show Investigation cards, and gather all unrevealed cards are shuffled and distributed evenly among the players.

Reveal Cthulhu, and the Cultists instantly win. Reveal all Elder Signs, the Investigators win. If you wish to play multiple rounds, the losers in each game get Insanity tokens. Get 3 tokens, and the night is done with the winner(s) being those most sane.

Don't Mess with Cthulhu Deluxe is a new edition of the allows up to 4-8 players.