The Yvaldeysean (Sea-King) Empire was made up of a set of “tribes” of the lords of the Seaborne Isles, each tribe ruled by a “King” and originally organized into an empire ruled by the high priest of Elancil and their hereditary house.
The Beginning of the End of Empire: After the Cosheus Abyssal was formed, the great “world wound” where the horde of demons was cast down in The Sundering/Bale Times, the coastal settlements of the empire were wiped out in massive tsunamis. Although this was not the end of the empire officially, it was the even that precipitated the great loss in power and resources which eventually allowed its enemies to bring about its demise.