Catan: Cities and Knights is the most complex of the Catan expansions and the one that most transforms the original game, making it more strategic and also increasing the length of the games. Therefore, it is only recommended for experienced players eager to go beyond the casual, family game. Games of Catan: Cities and Knights are played with 13 victory points instead of the usual 10. One of the most important changes in this expansion is the so-called event die. With each roll of the dice, players, in addition to the two dice normally used, will roll a third die that may result in the barbarians advancing on their expedition to Catan, or in the players being able to obtain progress cards if their city is sufficiently well-developed. In Catan: Cities and Knights, players can protect themselves from the robber and its effects by reinforcing their city walls. They can build these walls by paying two bricks, thereby increasing the maximum number of cards they can have in their hand when the robber appears. Another way to protect against robbers is through the use of knights. In this expansion, development cards no longer exist, so to acquire knights, players must purchase them directly. These knights are placed on the board and can be used to ward off robbers, cut off other players' trade routes, protect their own crossroads, or fight barbarians.
 Every time the barbarians arrive in Catan, all players must combine the strength of their knights to confront them. If they fail, those players who have contributed the least to the overall effort will see one of their cities razed. The last major addition to this expansion are the three new materials: Paper, Cloth, and Coin, which can only be obtained in cities bordering Forests, Meadows, and Mountains, respectively. These new materials allow cities to progress and make it possible to obtain new development cards, as well as the most advanced cities in each of the progress types to achieve Metropolis status. Achieving this status grants players 2 additional victory points.