United Kingdoms

Well, they aren't exactly "hidden," but they aren't very "open" either, as the inhabitants of the kingdoms interact with them very little. It is a large elven country governed by various influential organizations – religious, military, magical, and others. They pursue different interests but manage to reach agreements without resorting to infighting. Currently, they represent the main antagonist of Astromeria.

Spoiler: The history of this country begins with the military campaigns of knights from a certain island nation.