This is when a tribe, a caste, an ethnic group, or even an entire species is associated with the clerical duties of a religion. The reasons can range from simple tradition, to genetic and/or socio-cultural predisposition for religious activities, to a supernatural pact between that group and its respective deities.
Can be a subtrope to Planet of Hats.
- In The Belgariad, the Mad God Torak divided his Angarak followers into four tribes: the Thull serfs, Nadrak merchants, and Murgo warriors each have their own countries in the West, while the Grolim priests run his Religion of Evil in all of them. Even other Angaraks widely fear them, since they have a lot of discretionary power in conducting the religion's large-scale Human Sacrifice.
- In Courtship Rite a Lost Colony is divided up into economically (and eugenically) specialized "clans", with tribes of priests such as the protagonists' Kaiel clan and the rival Mnankrei, ruling.
- In John Carter of Mars, the Holy Therns are an society of White Martians self-appointed as high priests of Issus, and responsible for luring all other Barsoomian races into their domain so they can be enslaved. Subverted when its revealed the Therns are manipulated by another race entirely controlled directly by Issus, who commands their men to prey on their females.
- According to The Legend of Zelda: Breath of the Wild, the Zora race are associated with religiousity. One Hylian character in Rito Village explicitly labels them a "spiritual" people compared to others. The Tarrey Town sidequest tasks you with finding a Zora whose name ends in "-son" who can officiate a wedding because of this, and the fact that the Zora you do bring along was in fact a retired priest is considered by the quest-giver to be more of an unexpected bonus than an absolute requirement. And while it's not said as explicitly as with the Zora, the Sheikah are also depicted as having a very clergy-oriented culture based in large part on their devotion to Hylia and all their self-mummified monks waiting in the Shrines.
- The Shrouded Isle's sole village is a cult- as in, there's no distinction between villagers and cultists. Everyone has duties to the cult, everyone belongs to it, and the leader's political advisors must also carry out spiritual responsibilities such as penitence and book-burning. Even the village's children are tortured in accordance with Chernobog's will- although they are not told of the Human Sacrifice that occurs every season.
- Warhammer Fantasy: The subspecies of Lizardmen are devoted to various duties: Skinks are bureaucrats, skirmishers and priests, Saurus are warriors, Kroxigor are Dumb Muscle, and the Slann are extremely powerful wizards.
- Warhammer 40K: Tau society is divided into five Castes, each with a different function: the Earth Caste are engineers and scientists, the Air Caste are pilots, the Water Caste are diplomats, the Fire Caste are warriors, and the Ethereals lead the rest, possibly using mind control.
- The Levites in Orthodox and Conservative Judaism are the tribe from which priests are traditionally chosen.
- The Brahmin caste in Hinduism.