There was no more prominent or influential political, cultural, and military power on the current state of affairs in Domum than that of the Third Imperium. A massive empire that spanned virtually all of the continent of Partum as well as great swaths of two other continents (Tantam to the east and Arcanum to the south), the Third Imperium shaped the way of things for nearly three thousand years before falling apart with surprising speed.
Certainly there were multiple reasons for this failure. The Third Imperium had expanded as far as it could with the resources it had at hand, and was beginning to encounter stronger and stronger enemies as it pushed outward. Enemies within began to become more active as well, both petty and lofty in motive. The ruling nobles of Forkanza, especially the great houses of the Imperium’s capital Gothortus, started to war against each other with assassinations and open battle between estates. The last ruler of the Third Imperium, Inertis the Weak, was the most poorly equipped ruler ever known to history. He was a prideful, boasting narcissist that lacked common sense or any political savvy whatsoever. Immediately after being installed as the Imperator he was being undermined by everyone around him. Whereas it would have taken decades if not centuries to bring down the Third Imperium by normal means it was proven beyond a shadow of a doubt that a truly shoddy ruler can destroy their own empire much more effectively than any invader if allowed. Inertis was assassinated publicly by the most powerful nobles in Gothortus, including the patriarch of the Holy Imperium Church who managed to get in several well-aimed stabs on the flailing and defeated inept Imperator. Civil war broke out among the nobles in earnest and Forkanza continues to be a fractured peninsula filled with squabbling city states to this day.
The city of Gothortus suffered the most from this civil war. Alliances between noble families were forged and shattered during the next hundred years as huge sections of the empire fell away to revolution or invasion. Ultimately there were only three houses left standing; Vandocci, Andolinni, and Stragesta. The lords of these houses were so engulfed by their hatred for each other that they became undead of the worst sort. Living creatures fled the horror of Gothortus or were absorbed into the vile and despicable hell on earth that the area became. These houses continue to fight one another to this day. Undead soldiers bound to a duty they can no longer deny are forced to fight, be destroyed, and then rise again to continue the struggle. The three lords of Gothortus use other city states and their resources as pawns to keep trying to best one another all across Forkanza.
It should be noted that all of western Partum to one degree or another owes it’s existence to the Third Imperium. Carloman the Great raised a great army of elves and men to rebel against the yoke of the Imperium to forge the nation of Fanolania. Four great lords united their armies to do the same in creating Geldenreich. And to the southeast the Patriarch of the Holy Imperium Church decreed that the Diosian Lodge be given autonomy in establishing control over what would become the Sikilian Confederation as a bulwark against invaders from Tantam. Even the small and chaotic little states of central Partum owe their origins to the failures of the Third Imperium to unite or conquer them. It is quite incredible to see what can happen when a people chooses an ignorant and self-absorbed man to govern them. Soon enough everyone is scrambling to save themselves are decrying the rapid decline of morality. If you were taken by surprise then you clearly hadn’t been paying attention, the Third Imperium had not been paying attention.