Underleague is a fantasy card game set in the smoke-filled city of Helgarten. Players take on the role of breeders assembling a stable of fantastical creatures and mechanical monstrosities, and entering them into illegal pit fights against each other - while also betting on the outcome of these bouts.
In Underleague, each player has a 30 card creature deck. During the game, 3 of these cards will be in play as that player's current stable. Each creature has a unique effect, and a value which contributes to a player's over-all victory points. Each round, players use these creatures to challenge their opponents', while betting on which creatures will win and lose fights. Winning fights results in additional victory points.
There is an additional shared 250 card strategy deck, from which players will draw scheme cards and equipment cards, which can be used to impact the results of fights and the flow of the game. The more correct bets a player makes during a round, the more strategy cards they will be able to draw in the next. The first player to achieve a total of 20 victory points wins the game.
Underleague contains a total of 30 unique creature cards and 40 unique strategy cards. In addition to the basic game mode, it also contains rules for 'constructed' and 'draft' play.