"This does not match any known piece of architecture in the Ministry of Colonial Architecture's blueprint collection."
A player will see "A creepy shrine is being constructed." in the Notification Window. shortly before construction is completed. Shrines are usually constructed near the boundary of the fog of war. Shrines will only be constructed by Cults that contain three or more members. Non-cultists will become upset if they witness Cult worship at a shrine, and cultists will become ecstatic.
A Cultist who is Performing the Act of Murder will first go to a shrine to retrieve a Ritual Dagger, before attempting to re-enter town to murder colonists.