Geas is a card game intended to be played with the Tarokka deck included in the Forbidden Lore boxed set. The deck consists of 54 cards: four suits of ten cards each numbered 1-9 plus an "archetype", and 14 unsuited cards.
In each hand players are dealt five cards and take turns drawing a card from the deck or discard pile and then playing or discarding a card.
A suited card can be played as part of a player's adventuring party or to attack a member of another player's party. A party consists of one card of each suit, preferably all of the same alignment: the numbered cards are divided into good, neutral, and evil alignments while the archetypes are wild.
If a player has a single-alignment party they can play an unsuited card, which is an adventure the party completes to gain a point.
A hand ends when the deck has been gone through three times. The game ends when each player has had a chance to deal.
Optional rules allow for such things as two-dimensional alignments (adding the chaotic-lawful axis).