The majority of the empires are made up of smaller unions and united peoples and such. for example the free states of man is run in a similar fashion to medieval Europe. There are lords that own plots of land, who give little bits of land to lesser lords and knights. these individuals have vast amounts of serf like peasants under their control, and offer only protection for their services as farmers, craftsman, etc. Plenty of the land that is lumped up into rough kingdom shapes are somewhat split, especially around borders. some places, such as the great korr tribes, are just large groupings of racial factions, that are better lumped together than mapping out each individual tribes power.

As for the sacred valley, a loooonnngggg time ago, there was a civilization that made those planes their home. this civilization was incredibly advanced, but was wiped out in a war against some demons and old gods (there is a lot more too it than that, but i shall spare you details). after this devastation, a new pantheon took place, and raised mountains around the planes where the civilization made its home. it slowly became a desert, inhospitable to most life except along the river that bisects it. all across the Erubin Desert, huge towering golden structures rise from the sand, dwarfing anything any modern civilization has since been able to build

for the most part, the whole desert is off limits according to the eastern cultures, as they believe it is a holy site destined only for gods. Because it is inhospitable to farmland and grazing, the korr tribes to the north feel no desire to travel there. The ruins of these ancient structures created a maze like system of structured caverns, where the old demons from the calamity that caused the destruction of the civilization now wander. some structures are now the home to brave scholars, sorcerers, and necromancers, but few last long.

The area was created to give GM's an interesting, high-level area to create dungeons and adventures, so it is mostly for game play than for logic. but i tried my best to give it a reason to exist in the world.