A Petrificatus is a Promethean who completes a Role in their Pilgrimage and refuses to move on (despite Wastelands, Firestorms, and the warnings of various Qashmallim). After a year and a day, their Azoth gutters out and their Pilgrimage stalls, causing them to lose their free will and intelligence. They become mindless, drone-like automatons that only spring back into life and action when performing actions related to their Role. They do not have an Azoth rating and cannot manipulate Pyros, which means they do not cause Disquiet or wake Pandorans.
Petrificati are still somehow capable of performing the generative act, but can only create Pandorans or more Petrificati, not true Prometheans. A Petrificatus created in this way will instinctively adopt a Role that suits the body's former life. Creating new Petrificati produces Vitriol, making the Stuck a target for alchemists, Centimani and other predators.