The Orygmoiea are the first Culture I have created for the 5e Campaign Setting I'm working on.

An extreme isolationist Theocracy, the Orygmoiea are the only Culture with an inherent connection to the Myr. Via an unknown cosmic interaction thousands of years ago, the Orygmoiea learned a method by which they could tap into the Myr without the aid of technology. Treating this discovery and their newfound connection with the Myr as a sign of a divine spiritual and cultural path, they retreated progressively deeper into the inhospitable cold of the Steeps region. They refuse contact with the outside world on principle and kill on sight, believing outsiders to be Godless savages sent to disrupt their righteous purpose.

Orygmoiea spend their lives in enormous vertical cities, twice as large underground as they are above. A mandated symbol of loyalty is the total removal of their hair, thereby also removing any natural insulation they would have against the fatal cold temperatures should they try to leave the protection of their cities.

The low light levels underground have caused the Orygmoiea's pupils to greatly enlarge and occupy most of the front face of the eye. To combat the total darkness of the deeper levels, however, the Orygmoiea use unique luminescent tattoos to identify each other, and luminescent painted architecture to navigate.