Called "the City of the Necromancers," Yethlyreom is a city-state that rose to power in the wake of Thule's imperial collapse. Originally a pilgrimage site dedicated to Donn, god of the dead, Yethlyreom was swamped with migrants, refugees, and other displaced persons seeking safety and stability, causing its population to swell beyond what its walls -- or its government -- could comfortably handle. The clerics of Donn attempted to make the best of the situation by instituting taxes and fees designed to eject the lowest orders from inside the walls of the city. The clerics' plan worked and soon a sizable shanty town grow up around Yethlyreom, inhabited by those unable to pay the levies.
Events took a turn for the worse when an army of bandits made of former Thulian legionaries appeared in the countryside, bound for Yethlyreom. Those outside the walls begged to be allowed inside to protect themselves, but the clerics of Donn did not hear their pleas. It was then that a magic-user by the name of Bion appeared, along with a small band of comrades and apprentices. These magicians promised to protect not just Yethlyreom but also the shanty town outside it and did so -- by calling up an army of the dead. Skeletons, zombies, and other types of undead were brought forth from the vast necropolises surrounding Yethlyreom. Under the command of the necromancers, these creatures drove off the bandits and saved the city.
It was then that Bion and his companions, at the head of an army of both undead and peasants, stormed the walls of Yethlyreom and cast down the clerics of Donn, claiming the city for themselves. Under Bion, all clerics of any sort were banished from inside the city's walls -- an ironic turnabout considering recent history. Necromancy was practiced openly and anyone, regardless of social status, who demonstrated the ability to work magic would be taught to do so in return for service to the city-state. Since that time, Yethlyreom has grown powerful and influential, rivaling even Adamas. It is now one of the major power centers of the post-Thulian world.