Cult of the Lamb is an action-adventure strategy game developed by Massive Monster. Players assume the role of a possessed lamb tasked with building a cult in a land of false prophets. This involves gathering resources to construct buildings, performing rituals to appease gods, and delivering sermons to followers. The game world is randomly generated, requiring players to explore diverse regions, combat enemies, and defeat rival cult leaders to gain power and spread their influence.

The "Unholy Alliance" expansion introduces local co-op gameplay, allowing two players to control the Lamb and a Goat. This expansion adds new tarot cards, relics, buildings, follower traits, and quests, with some mechanics designed to leverage cooperative play. Further expansions like "Sins of the Flesh" and "Relics of the Old Faith" add new progression systems, combat options including new weapons and relic abilities, post-game challenges, and customization for followers.