The Eastern Empire was founded by a group of stranded mercenaries and regular army troops in the years following the Mage Wars. They were originally part of Urtho's forces, but were cut off from the main body of the army after General Shaiknam's betrayal. During the mass evacuation from around Urtho's Tower, they somehow received word to move to safety farther east. They were passing through their evacuation Gate when the shockwave of the Cataclysm hit them. It warped their Gate, throwing them even farther to the east. Where they landed became the core lands of the Eastern Empire. While this is never mentioned in the official histories, some memory of the Cataclysm has lived on in superstition which warns of unspecified danger in the west. The strength of belief in this superstition is why the Empire expanded as far as possible in every other direction before turning to conquer its western neighbor, Hardorn. The same superstition is also why Baron Valdemar chose to take his people west when the they fled the Empire centuries before.
The Empire is a military and magical powerhouse stretching from the eastern borders of Hardorn and Iftel to the Salten Sea. Ruled by the Emperor, the Iron Throne is passed to the Emperor-elect in the final years of an Emperor's reign. Administrations can last upwards of a hundred years, for the Emperor must be a mage of at least Master-class, and as such, has access to life-extending magics.
Until the Mage Storms, the Empire was known for their reliance on magical contrivances, such as mage lights, and prolific use of magical Portals, a sort of permanent Gate. The Mage Storms effectively eliminated the use of these portals and other devices, causing massive chaos throughout the Empire.
For centuries the Empire conquered its neighbors, incorporating nation after nation into the Empire. They followed the same tried and true formula to assure victory in their conquests. First, the targeted nations government was destabilized and chaos was encouraged with the goal of making life hard enough for the common people to build up anger and resentment toward their government. Then, when the nation was in a shambles, the Imperial Army was sent in with a strategy of divide and conquer. The shock troops took a calculated chunk of terrain. They were followed by consolidation troops that took care of any remaining resistance. Once the area was pacified, holding troops arrived to repair and build fortresses, roads and industries. They were followed by the administrators and Imperial Police who imposed Imperial Law on the newly minted citizenry. The last wave of conquest was the Imperial priests, who established veneration of the Emperor alongside whatever religion was found natively in the area. Then the whole process began again on the next chunk, with each successive line of troops sweeping across in waves.
Once a nation was fully incorporated into the Empire, they faced Imperial taxes, which amounted to sixty percent of their annual produce, and was adjusted each year. The army also conscripted all young men between sixteen and twenty-one years old. However, by the time they were faced with these unpleasant realities, conquered people usually felt it was worth the benefits they received.
This group is culturally similar, and vaguely analogous, to the Roman Empire.