SKU: 13213
UPC: 841333113414
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Immerse yourself among the passengers and crew of the SS Atlantica in this game of hidden loyalties, intrigue, and paranoia for three to six players set in Fantasy Flight's Arkham Horror universe.

The year is 1913. The passengers of the SS Atlantica fully anticipated a calm journey to Boston, Massachusetts, with nothing out of the ordinary to look forward to. However, strange nightmares plague them every night; rumors circulate of dark shapes following closely behind the ship just beneath the waves; and tensions rise when a body is discovered in the ship’s chapel. This voyage began like any other, but now it seems that the Atlantica may never reach its destination.

Some of you are humans, fighting for the survival of the ship; others are traitors, hybrids sent aboard the ship by mysterious beings to ensure that it never reaches port! Because player loyalties are hidden, determining who is friend and who is foe is critical to winning a thrilling game of Unfathomable.

Lurking within the depths of the Atlantic Ocean are a swarm of vicious, unspeakable horrors, the Deep Ones. For reasons unknown, they have set their sights on the Atlantica, and their minions have infiltrated the steamship to help sink it from within.

In Unfathomable one or more of you assume the hidden role of one of these hybrids, secretly sabotaging the efforts of the others on the ship. It might mean the difference between a successful voyage and a sunken ship.

Do you like liar games but with even more tactics and strategy than your usual social deduction party game? Unfathomable will be perfect for you!

Unfathomable takes place in the Arkham Horror Files universe based on the Cthulhu Mythos, and it takes place many years before the events of the Arkham Horror board game and card game. Because of this, this game features a full cast of brand-new playable characters, each of which has never been seen in the Arkham universe before.

Are you a friend to humanity or a hybrid saboteur?


  • 1 Game Board
  • 4 Resource Dials with Plastic Connectors
  • 1 Eight-sided Die
  • 22 Monster Figures (1 Mother Hydra, 1 Father Dagon, 20 Deep Ones)
  • 10 Character Standees
  • 1 Travel Track Token
  • 1 Ritual Track Token
  • 10 Character Sheets
  • 3 Traitor Reference Sheets
  • 6 Player Reference Sheets
  • 1 Captain Title Card
  • 1 Keeper of the Tome Title Card
  • 10 Feet Cards
  • 20 Spell Cards
  • 20 Waypoint Cards
  • 20 Item Cards
  • 9 Ship Damage Cards
  • 126 Skill Cards (21 each of 6 different types)
  • 14 Loyalty Cards
  • 70 Mythos Cards
  • 9 Passenger Tokens
  • 4 Traitor Rings
  • 1 Current Player Token


Players: 3 - 6
Ages: 14+
Runtime: 2 - 4h
Designer: Tony Fanchi, Corey Konieczka


Learn to Play (pdf)
Rules Reference (pdf)