The Devout Villager is a normal citizen, with one exception: they can never change role.

When a role changing ability affects the Devout Villager, it fails. If the infecting wolf tries to infect the devout villager the infection fails and nothing happens. If a vampire tries to demonize the Devout Villager it happens normally, however if the Devout Villager is attacked they will die instead of turning undead.