Cesynia

Cesynia is a wide region of fertile lowland plain stretching out to the north of the Saulean Sea. It has long been a part of the Phyridian Empire; its southern reaches, along the coast, are considered a part of the empire's core provinces. 
Cesynia is crossed by many rivers, the two most important of which are the Ziva and Ontos. Both run generally north to south, converging to form the Zivontos before emptying into the Saulean Sea. To the north, the Cesynian plain merges into the marshy flatlands of Baajir (wherein lie the headwaters of the Ontos), which then give way to the vast Plain of Tethas.