Monks and Mystics is the latest expansion to Crusader Kings II, the hit medieval grand strategy role-playing game from Paradox Development Studio. In Monks and Mystics, the religious aspect of the game is further explored with new mechanics and character associations that can tie a faith closer together or render it asunder.

The major feature of Monks and Mystics is the addition of Societies – secret and otherwise. Characters can join monastic orders, secret cults and Gnostic heresies. As the society gains members, it gains power and prestige for its leaders. Societies open new actions for characters and can lead to new event paths.