If your gaming group is growing, this extension is a lifesaver. It allows you to bring up to six players into the complex world of Cities & Knights, so no one has to sit out and watch. It introduces a "Special Building Phase" that lets everyone build between turns, which keeps the game moving fast even with the extra people.

Just remember that this is an extension, so you will need the original Catan game and the Cities & Knights expansion to use it.