A boardgame of 19th-Century Mars, set in the Space 1889 RPG universe, players take the role of one of 10 adventurers leading an expedition into the mines of the sinister Martian King Gnaashriik in an attempt to rescue slaves and gather up loot.

Each player's character has a special ability useful throughout the game plus an special way to score extra points (For example, if Sir Colton-Haynes recovers the Ancient Tablets, he scores 10 points instead of the normal 4).

The board is made of tiles which are shuffled and placed face-down to form a mine shaft 5 levels deep.

Each turn players move through the mines, turning over tiles to create a series of passages and rooms, discovering and fighting off Martian baddies, and grabbing whatever goodies they can find.

There is a deck of cards that drives discoveries and can allow characters to find hidden passages, set off a trap, or wander upon an extra nasty combat.

The deck is also the endgame timer. Once it is depleted, players rush to the surface to end the game.