This land is flat, wooded in areas, humid, hot in the summer, and bitter in the winter. The common racial stock that populates most of the continent originated here. The people are of moderate height, solid build, olive coloring, and dark hair. The Great River that separates Cassile from the rest of the continent is difficult to cross, so once migrants from Cassile reached the more fertile Karrim and the more scenic and temperate Dabion, they were reluctant to go back.
The racial stock seen in the Five Countries (except Azassi) originated in Cassile. About 500 years before the Common Calendar, these people began to move out from Cassile. Prior to this, Sages and Magi lived in the other areas; when Cassilians crossed the Great River, most withdrew to Sor'rai.
Schools of anthropology and archaeology developed in Cassile about 100 years before the arrival of Biorans. They studied the early material culture and attempted to trace the migration of people across the river, as well as the arrival of the peoples of Biora and Azassi. A few decades before the start of the Common Calendar, a plague struck Cassile and cut the population drastically.
Because the plague struck cities hardest, and cities were the centers of study, people in the outlying regions mistrusted both urban life and scholars. The native animistic religions refined and strengthened, as outlets for dealing with the plague. By the time the Bioran travelers arrived they were largely entrenched. The Biorans found no interest in education among Cassilians; they crossed the Great River in the north, near the Kian Pass, and had little contact with them.
Religious houses in Cassile practiced variations on a general belief in a harsh higher power. Many taught that hardships were punishment for transgressions; others taught that the plague had been a test that weeded the weak from the strong and righteous. The Pure Transcendentalist movement diminished the importance of the material world by focussing on the spiritual.
As the countries were torn by the controversies of Bioran learning, the religious houses in Cassile attracted more ascetics who attempted to escape violence. The populations of these houses swelled, and newcomers often brought their conflicts with them, sometimes leading to confrontations in the common rooms of monasteries.
In 517, the monk Nanian, of the Pure Transcendentalist house, had a revelation that peace could only be achieved by eliminating the source of the controversy: science and learning. His followers went on to convert all the Cassilian houses, and Nanianism gradually spread throughout the other countries.
Followers of other religious traditions left the religious houses but continued in their own traditions in small, home-based settings. These practicioners were often solitary, teaching their immediate families and few others; sometimes entire villages practiced a certain religion. These unorthodox practitioners were not accepted, but they experienced little hostility from Nanian houses with their focus on immaterial things.
Nanianism underwent changes after 523, when Dabion instituted it as the state religion. Dabion incorporated Nanian's philosophies into their system of justice, and gradually turned toward orthodox interpretations of the religion, rather than the original teachings of Nanian. This created a rift between the relatively small number of houses outside of Cassile and the monasteries in Cassile, which preserved a more mystical orientation.
During the age of Mandera's prosperity, Cassilian villages were often exploited for resources, not without profits. Mandera established a few factories in Cassile, and recruited Cassilians to work at factories in Mandera, as well as culling wood and coal from the land. Being more willing to work with the population, Manderan industry leaders bargained with Cassilians, not urbanizing or stripping the country more than the people would allow, and paying burghers for their use of the land. This prosperity led to the rise of Minstrelsy, a movement that arose in the villages and set itself strongly apart from monastic mysticism by praising worldly things. The Nanian houses became even more ascetic.
Some industrialism continued even after the fall of Mandera. The Justices continued to demand rich, if colorless, fabric, and Cassilian factories were used to produce it. The procedure for making velvet is time-consuming, requiring the weft thread to be raised with rods and cut. Weaving required two to three people and might produce a few inches of fabric per day.
The suppression of Nanianism by Dabion closed all the religious houses, in often violent confrontations. The limited spread of Nanianism beyond Cassile was also halted. The last few schools of Minstrels that remained after the end of Mandera's patronage also dissolved, and only the villages were left. These were exploited by Dabion, more harshly than Mandera had, but Manderan officials were often employed as mediators because of the extreme distance from Dabion. This mediation buffered the harshness of the new Dabionian policies somewhat, and because Cassile's population was smaller, violent confrontations like those seen in Karrim did not occur to the same extent.