Expand your gaming experience with the super-colored, super-fun, super-crazy Dice Expansions for Railroad Ink Challenge!

Every expansion add a new layer to the game, changing it in unexpected ways and allowing new strategies to be explored and mastered, even for seasoned Railroad Ink Challenge players.

Underground is a single 4 dice expansion. Manage an underground network of Subways and Water Pipes. You can use the Underground dice either as an Expansion to the base game or as a Standalone game.

To play with the Underground dice as an Expansion, you need two boards for each player: one board for the Surface and one for the Underground. You will play alternating between Surface and Underground rounds for a total of 14 rounds: 7 Surface rounds and 7 Underground rounds. Start with a Surface round, following the normal rules of the Railroad Ink version whose boards you chose as the Surface boards.

During an Underground round, the Underground dice are rolled and every player must draw the results of these dice on their Underground board, following the Underground placement restrictions.