Knights of Ten is primarily a game for two, but can also be played by four competing in teams. You're trying to collect as much gold as possible each round, and the player (team) with the most gold after the predetermined number of rounds wins.
Each round, players start with seven cards in hand; cards feature numbers from 1 to 10, as well as negative numbers, cards that can be either positive or negative, and special plays such as the dragon and wizard. One player leads by playing a card to her "horde" (the table in front of her); if she plays a 1, she can play again immediately. The next player must follow – playing to his own horde first – and have an equal or higher total in his horde at the end of his turn. If he can't, he loses the trick; if he can, the opponent gets to play again and play continues back-and-forth until one player loses.
Whoever wins collects 1 gold, plus 1 Gold for each Gold card in the pot. The winner draws one card and either keeps it or keeps the next card in the deck; the loser draws two cards (one of them being the card left by the other player, if any). Play continues until all 16 Gold have been claimed, at which point a winner is determined for the round.
In a four-player game, you and your teammate share a horde and take turns playing into it.