From the publisher's website:

Three-Dragon Ante is a card game developed by Rob Heinsoo, and published by Wizards of the Coast in November 2005. The game is a combination of luck and skill, and blends concepts from traditional card games such as poker, hearts, and rummy. Based on Dungeons & Dragons, it is intended as a game in its own right or as an element in a role-playing campaign. The game is recommended for 2 to 6 players, each of whom begins with 50 points (called gold). The game is divided into gambits in which gold is added and detracted from the stakes (similar to the pot in poker). Each gambit normally has three rounds (four or more can break ties). In each round, players play cards in front of them (comprising their flight). The strongest flight is the one with cards summing the highest numerical value. After each gambit, each player draws two cards. All ante cards and flights are then discarded. When the last card is drawn from the pile, you shuffle the discard pile and it replaces the draw pile. In a gambit, players initially choose a card from their hand to ante-up (see poker). The highest ante determines the amount of gold every player must pay to the stakes. The player with the highest ante plays first, triggering the special ability of their dragon. The special powers of each card varies from allowing players to draw more cards or steal money - from the stakes or other players. In general, good dragons allow players to gain cards, whereas evil dragons allow players to get more gold from the pot or other players. Mortals are especially powerful, so players often maneuver to trigger their mortals' special power. After the first card in the round is played, players play cards in clockwise order. If the value of the card is less than or equal to the one played before it in the round, it triggers. Otherwise, it does not. The highest dragon in a given round determines the leader of the next round. The first card played in every round always triggers. Most gambits end after three rounds, though occasionally a tie extends it to four or more rounds. In either case, the strongest flight (sum of the values of each player's three cards) wins. Additionally, special flights (color or strength) allow players to earn extra gold or cards. Players must buy cards from the deck if they run out of cards. The cost of new cards is determined randomly by flipping the top card of the draw pile; the player pays its cost in gold. This commonly happens, since replacing cards can be difficult. The game ends when one player's hoard runs out at the end of a gambit. Optional alternate endings are also suggested in the rules.