Castle Crashers is set in a fictional medieval universe. It begins with four knights attending a party in a king's castle. During the party, a dark wizard arrives, stealing a mystical gem and capturing four princesses. The king sends the knights to retrieve the gem, rescue his daughters, and bring the wizard to justice. The knights encounter several enemies along the way, including other knights, multiple encounters with a cyclops, thieves, a giant "catfish", factory workers, monstrous oceans with ninja pirates, and alien invaders. As the knights progress they succeed in rescuing the princesses, and ultimately the journey culminates in a final showdown with the wizard. The knights emerge victorious from the confrontation, having defeated the dark wizard, rescuing all of the king's daughters, and recovering the mystical gem. The knights then ride the reclaimed gem through several empty battlefields on their trip back to the castle. At the castle the king brings one of his daughters for one of the knights to kiss, her face veiled throughout the entire game. As with previous levels, the players fight to the death to claim a kiss from the princess. However, when the winner tries to do so this time, the princess is revealed to be a clown that blankets the screen.