Phantia

I think I finally managed a reasonably short one!
Mostly because I'm tired, which really cuts down on the 'constantly thinking of stuff to add' issue.

The Hall of the Dead is, metaphorically, the center of the world. More literally it is (unsurprisingly) where one can find the dead (or the important dead, anyway - the rest are scattered across the infinite featureless .  plane beyond the Hall).
The dead, in one sense, are completely unable to influence  the world - that sense being the physical sense. The dead can’t even communicate with the living without help from someone on the outside. But the thing about the dead is that there are a lot of them. And some have been around a very long time.
And so, the dead have money, they have experience, and they have knowledge. It shouldn’t really be a surprise that they’re in charge of the state of Phantia (which escapes being called a continent-spanning empire by dint of the fact that it doesn’t have an emperor). Few governments are able to take on the entire rest of the country in an all out brawl, so their physical limitations are less of an issue than they might be.
Instead, necromancers exist as a kind of civil service in Phantia, communicating to the people the wishes of the dead.
One might expect, given what normally happens when a small group claims to speak for the rulers, that their decrees might be a little… diluted. However, it is a fact of the universe, and no less so in Phantia, that everyone dies eventually. Fear of what might come afterward seems much more immediate when ‘what comes afterward’ is a few seconds of simple chanting away, and capable of informing you exactly what it is going to do to you if you don’t start listening.
Not that they can do much directly. For the spirits of the dead to hurt each other, or even to cross the barrier that separates the Hall of the Dead from the plains beyond, they need to be empowered by a necromancer. But death lasts an eternity, and the dead can hold a grudge that lasts eons. The chances of them finding someone to carry out their threats eventually are high.
Of course, not everyone is deterred from infinite worldly power by possible future consequences. So until a few hundred years ago, the necromancers would occasionally quietly launch a coup, and start substituting their own orders for those the dead had been giving.
The problem each time was that not all necromancers work for the government. And whilst one might be able to trust one's own students and heirs to ignore promises of wealth, and protect one from the wrath of the dead, independent necromancers were less certain. And attempting to get rid of them was not only impractical, but made what was being done rather obvious.
So the coups never lasted very long, in the grand scheme of things. A few decades at most, before the current crop of necromancers were gently reminded of their place by the agonised screams of their predecessors.
But a few hundred years ago, things changed, and not in favour of the necromancers. A newcomer to the Hall, named Alexos came up with the idea of splitting the service into branches. Now, there are nine such branches, each with a grudge against all the others, and kept in a kind of working harmony only by the threat of mutually assured destruction. An alliance between all of them has so far proven impossible, and lies about what the dead have actually said tend to be interpreted by the other branches as attempts to seize power.
As for the dead themselves, their main concern is power. For the simple reason that those whose main concern isn't power, tend to be ejected from the Hall by those who are more focused on it. They rule well enough - to avoid being overthrown, to gain favours from the living, even to satisfy their own egoes. But this is not their main concern. Their main concern is the Byzantine politics of the dead - it is making gains in their own positions, whilst weakening their enemies, or even throwing them from the Hall entirely. They seek power, not for any purpose beyond this: that they need some way to pass eternity.