Oss is a skill game based on jacks, with players trying to perform certain tricks in between tossing their jack into the air and catching it.

The game lasts four rounds, with three solo challenges and one duel challenge laid out each round. Each player has a hand of five tribe cards (from a set of eight), and going clockwise from the chief, each player lays down a tribe card in front of one of the solo challenges. If two players play on the same solo challenge, their tribe cards are moved to the duel challenge, then all other tribe cards are placed on solo challenges.

Starting with the chief, each player attempts to perform the trick shown on the challenge, with the value of the tribe card played showing how many jacks on the table must be used in the challenge. A challenge might have you setting jacks on edge, throwing a jack over a wall formed by your other hand, move jacks from the table into your other hand, and so on. If at any time, you fail to catch your jack, your turn ends — although you can twice discard a tribe card from your hand to replay the challenge. If you succeed, you keep the tribe card you played.

In a duel, the first player to complete the duel keeps one of the two tribe cards played.

After all solo and duel challenges are complete, everyone participates in a final challenge to determine who will be chief for the next round. After four rounds, players tally the points on the challenge and tribe cards they collected, and the player with the high score wins.

Reimplements: Knucklebones
Reimplements: Jacks