Unfathomable

To set up Unfathomable, place the main board in the center with the travel and ritual markers at their starting positions. Populate the board with deep one figures in the surrounding water spaces and specific decks. Shuffle the skill decks, mythos deck, damage deck, waypoint deck, and item deck, placing them in their designated zones. Create the chaos deck by drawing cards from each skill type. Players randomly select a character, receive their starting items and skill combinations, and take any assigned title cards like Captain or Keeper of the Tome. Finally, deal secret loyalty cards determining whether players are loyal humans or hidden hybrids working against the crew.

The game features a hidden loyalty mechanic. Human players work cooperatively to safely navigate the SS Atlantica to Boston, keeping essential resources like fuel, food, sanity, and souls above zero while defending against monster attacks and repairing ship damage. Conversely, secret hybrid players masquerade as humans while quietly sabotaging skill checks, causing crises, and pushing the ship toward ruin without blowing their cover until they choose to reveal themselves.

A player's turn consists of four sequential steps. First, they receive new skill cards based on their character's skill set. Second, they spend up to two actions to move around the ship, attack monsters, rescue passengers, trade items, use room abilities, or repair damage. Third, they draw and resolve a mythos card, which triggers a crisis requiring a shared skill check, activates monsters, and advances track markers. Fourth, they discard down to a maximum hand limit of ten cards before passing the turn clockwise.

There are no traditional victory points. Instead, success is binary based on the final game state. If the human players successfully accumulate twelve or more distance points from waypoint cards and reach Boston, all loyal humans win. If the ship sinks due to resource depletion, excessive ship damage, or a lack of available deep one miniatures, the hidden traitors win.

The game immediately terminates when any end-game condition is met. These conditions include the travel marker reaching the final space with at least twelve waypoint distance points accumulated (a human victory), any of the four resource dials dropping to zero, six interior ship spaces becoming damaged simultaneously, or the deep one supply running completely empty. Upon triggering any failure condition, players reveal their loyalty cards to determine the winners.