Morroc

For most of its life Morroc was the practical heart of the continent: caravans stopped here, cloth was dyed here, precious metal was worked here, and a chief governed the town separately from the capital. The people were famously unhurried and famously cheerful about it. Nearby stood the Sphinx and the Pyramids, which had begun to fill with things that should not have been inside them.

Then the seals under the castle broke. In a single night the town was torn open, the castle was destroyed, and the survivors fled north-west to the old ruins. The thing that had been buried there walked east into the desert, and the desert has not been the same since. The Continental Guard quarantined the ground it touched.