Land Between Three Rivers
Welcome to the land of Tridanus.
The Riverlands are the big fish in the Tridanus pond. They are a state with vast wealth and power, however this capital is focused almost entirely inward. It's not that they fear overextending, it's just that the political elite see little of worth outside the confines of their borders. While largely human in composition, their wealth does attract many outsiders which are tolerated to some degree, provided they know their place. They are currently ruled by the elderly Emperor Junzu of the Ten dynasty, a direct descendent of the demigod of the same name who saved the people of the Riverlands from evil two thousand years ago.
The Twelve Noble Clans
The will of the Emperor is enforced in the Riverlands by the Twelve Noble Clans, all of whom have sworn eternal fealty to his house. Like most lord-vassal relations throughout history, their loyalty has ranged from earnest to self-serving to token throughout various points in time.