Castle Merchants is a tile laying, hand management, pick up & deliver game. You play the role of a merchant peddling his wares to various castles in the land. Since all the merchants are offering the same wares for sale, the merchant who is able to reach a castle first can receive a higher price than those visiting in later turns.
You must manage your hand of path cards that you use to place paths onto the board, or to traverse the paths themselves. You may play any number of cards on your turn, but must be careful as you can only replenish your hand with a certain amount of cards regardless of how many you played. Whether or not you want to reduce your hand size to push on farther and beat your competition to a castle is just one of the decisions you'll find yourself making every turn.
Merchants must build paths wisely, for if you can't fully make use of the tiles you play, there is a chance that a competing merchant might be able to speed past you on the path and make his delivery to the castle first. Merchants must also be wary of possible rock slides that can make a path impassable and force them to have to change their plans and find a way around the obstruction. The first merchant to accumulate 18 pieces of gold is declared the winner.