The Imperium is a Theocracy, based around the veneration of their undead god, and the study of his philosophy. The Imperium is based around the great cities of marble in the deserts, the commercial quarters are raised on the tops of the great platforms, where all can see them, and they border the great administrative sectors that contain the massive palaces of the rich and power alongside the huge hives of humanity where the empire is really run from. Inside the massive tiered bulk of the structures lies the agricultural, populated, and industrial sections, with industry being arranged around the outside of the oft-times circular buildings, usually congregating on the mid-height levels. The housing is usually concentrated on the highest tiers of the buildings, and in the center on the lower tiers. At the very bottom there is the agricultural sections. Where the massive amount of food required to sustain these behemoths is harvested day and night in massive subterranean complexes.
Outside of the cities, the villages and towns lie. Most of these belong to one of the factions or clans that make up the political system. Infighting for land is not exactly uncommon, and independent villages are often protected by the forces of the empire itself. Most villages specialize in one thing, while towns can be experts in the production of dozens.
The army of the Imperium is unique. It is made entirely of the dead. Those whose spirits have passed on are given to the living, and are animated either to use as servants, or as soldiers. They are completely mindless, and are controlled by priests. The secret of making the reanimated who actually retain sentient, as well as the secrets of the making of most other reanimated besides basic soldier/servant fodder have been long lost. In battle they are well known for being one of the more terrifying armies to face, as they are eerily silent as they move into position, and they wear the face of death itself.
The magic of The Imperium is based around belief. By swaying the minds of others great magic can be achieved. The flipside of this is that one with a strong mind can resist their magic. But at a cost. They may survive the physical attacks, but their magic also targets the mind, and only those with great wills can escape unscathed.
It is also based highly around the forces of life and death. The priests have an affinity with souls, and can command, manifest, calm, and aid them. This is the reason why soul-takers and slave traders stay far away from their lands: The souls of slaves cry out for terrible vengeance, and souls taken cry for the reckoning of it's taker. The priests will not stop until justice is served, and with the souls of the dead lighting their way, few can stop them.
It is worth nothing that their religion is admant on it's stance towards slavery: It violates the dignity of life, and makes one wish for death's embrace. Both an abomination in the eyes of the church.
The Political system is technically a theocracy, but is made up of dozens of factions within and without the church. Whenever the old emperor dies, the choosing of a new one begins. The church chooses a handful of the worthy from any of the clans, who then begin a political battle, literally as often as not. The one who is crowned is just as often the one supported by the most families as just the one who survived.
The church is made up of 3 sections: The administrative, who control the inner workings of the church and basically run everything. The Political: They run everything on the outside, and make sure that the Imperium is under the control of the church; and finally: The actual Priesthood.
The priests are different from regular Nocturin. They always have some from of mutation, not counting their spiritual vision. The mutations differ, they can be as small as an odd eye colour, to the extreme case of the high priest Rincull, who has skin that changes colour going through the range of every known shade and every known pigment. The divine vision is different. All the priests are blind, but they can see using it. It paints the world in shades of the lightest blue, and white, and allows them to see, communicate and command not just the ghosts of the dead, but also the spirits of the world.
The priesthood are not usually seen by other races, although there is at least one priest in every village. Due to them being unseen, yet still commanding much of the political power of the empire, many rumors have sprung up around them in the other races. One of the fastest spreading is that they are anthrophages, eating the bodies of those of other races. This one one is true, and is in fact spread by the priests, as they desire the reputation for it's ability to scare away those that prey on the weak of the Imperium. The priests, being able to see the souls of dead everything, including things like insects and plants, are pacifistic. They do not consider use of their powers to be a breaking of this. Neither do they consider the eating of meat. (Livestock souls do not stay around long, aren't going to frighten them, and usually hang around the slaughterhouse.). The inside of the temples are never illuminated, as the spirit sight does not require light.
The Nocturin have a great many beliefs centered around death. The dead are more colorful then the living, both in clothing and in body. This is because of their belief that the dead are dead, and probably not too happy, and therefore deserve a bit of colour. The truth is that the skeletons don't really have souls, but the clothing does tell the soul of the departed that it is appreciated, and helps it to pass on. They also believe that since the earthly shell does not contain a soul any longer, wasting it would be a terrible ill. This is why they use skeletons. They also believe that death is not something to be afraid of, but one must be defiant, never want it, nor give into it, but always respect it. They believe in the celebration of life, as it is a wonderful thing, and one must never allow ones self to devalue it. Treat it as sacred, and never take it in bad conscience. They believe that slavery, of any kind makes one devalue life, and makes one wish for death. It also shows an unapreciation of life, and is a terrible, terrible torment.
They also believe in vengeance. That evil should have it's own torments repaid onto it. When a priest takes down a slaver, they make them experience all the horror and anguish of those they have taken, and the souls of the departed. Then they take them back to their temples, where they usually die within the hour and end up eaten.
Backstory (before the age without gods.): Long ago, this race had a much different god. He was a god of knowledge, first and foremost. He chose the Noct's after watching their exploits on another world, and he cared for them, perhaps moreso than any of the other gods.
In his people, he nurtured curiosity, inquisitiveness and intellectual focus, and they had something of a monopoly on higher learning. This lead to many schools of thought and philosophies being developed. These later evolved into full-fledged factions within the political system of the imperium.
Among these, one eventually grew to be dominant. Their philosophy was that both death and life are not profane, and beyond the ken of mere mortals. They believed that they can, and indeed must be understood, as not doing so would e immoral. They could promise the world, and maybe, just maybe; deliver it.
Eventually, it became apparent that the emergence of this was in doing something unexpected by all: It was diverting belief away from their god, which lead to his being unable to resist the assaults of another god, who dealt him such a blow, that not even his name can be remembered. This caused a massive shattering of the lands, and at the time, the gods had already pretty much abandoned the place.
They needed a hero. Shadin, the leader of the faction was a man who had a Presence. people believed in him, and he became leader. He managed to keep his civilization afloat during these times, and he managed to reform much of the society, by virtue of seeming like the only savior his people had. Such was their belief in him, that he eventually Ascended, becoming a god in his own right.
This was not a good thing. It did not go very well, what with the world being in such a state. Boundaries of reality were ripped, and dark things spilled into the world. A great deal of magic simply disappeared. All but the weakest, and most unintelligent if the reanimated came apart, but not destructively, and to top it all off, the tears that drained the magic and let the dark things in floated high above the cities of the Imperium, being very visible to all.
Post cataclysm history: Somehow, they survived. A churched formed around the departed mage, and became the leading force of the Imperium. During the age without gods, the Imperium became very distrusted by it's neighbors.
This caused a crisis due to the fact that they were unwilling to trade with them, and being in a desert, there are simply things that they need, but cannot provide for themselves. So until they were able to find and adopt agricultural practices utilizing underground plants, they almost died out. They grew bitter and resentful of the other civilizations, as outside of their homelands, they were blamed and hated and generally treated as being so undeserving of the life they hold so dear.
This eventually led to the whole thing becoming extremely insular. Eventually, trade did pick up, but things were never the same. Outside of their home, they were the worlds punching bag.
They rebuilt their lands, slowly. Surviving, but not thriving. They fought off the dark things regularly, and were in lands too undesirable, so they were not attacked as such. But there was something in the air in the cities, a slight hint of decay. They were slowly dying. All the fight was gone from them, and they were too stubborn to admit it. Then The gods returned, and thats where things start to get interesting.....
Artifacts: Temest Nex: The Codex of infinite wisdom: The only remaining relic of the nameless god. It contains all the knowledge of infinity, but is near impossible to decipher. It's the source of their industrial-era technology level.
The Flame of Forever: A flame that spring up from the location where Shadin left the world. If it were to go out, certain doom would result. It needs no fuel and freezes water, as it is deathly cold. It now rests inside the inner sanctum of the temple of the Dark Light
The Orb of Undeath: Allows the wielder to command the entire undead forces of the Imperium at once. Used by the Dead Commandant.
Tenryuubito: Hated by them, due to their flying in the face of their beliefs, and their relationship with death. The hate is mostly one way, as although they despise their slavery, that is about the only thing intrinsic to their culture that they hate.
Shehalash: Not a lot is known about them, but the church despises them for what attributes the priests can sense about them. The few of them who come this far south generally don't return.
The Sandriders: They have a very good relationship with the people of the sand, due to the similarity of the beliefs and habitats of most people. They have priests in the church, which serve as the mobile arm of the church.