The Arcadians

The Arcadians are an oppressively powerful coalition that rules over the entirety of their realm with an iron fist, so much so that they have even named Arcadia after themselves. The pact between the native humans and elves allowed them to lay claim to nearly everything they desired, and any who did not immediately bow to them were obliterated.

History
The modern Arcadians were all descendants of ancient Barcidians who fled the Eldrazi Scourge during the 3rd era. Despite their unity in escaping them, they quickly fell to anarchy deciding how to govern themselves. 57 years after they arrived, The elves, seeing the tenacity and unity in the humans, and seeing them as an effective means to their ends, proposed an alliance between them, utilizing their strength, combined with the elves cunning and natural affinity to the arcane. The humans agreed, and together they established their capital and began spreading their influence.

The only ones who bowed down to them were the halflings and gnomes, both of whom saw, even this early on, how powerful they were to become, and decided to join them than die fighting. Everyone else refused to kneel and fought on a united front against this coalition. The coalition, now referring to themselves as Arcadians, made an example of the orcs, quickly and efficiently exterminating them. The Dragonborn and Tieflings were in bad shape, and eventually surrendered into servitude, leaving just the Dwarves to fend of the Arcadians.

Battle of Mt. Belez-Al
The Arcadians initially made quick work of the Dwarves, forcing them to back up further and further into their mountain capital of Belez-Al, where the Arcadians ran into their first and only significant resistance. Due to the steep and narrow slopes up the mountain, along with the Dwarves network of ambush tunnels allowing them to attack from multiple angles, the Arcadians had to expend more resources and manpower than they were accustomed to, and by the time they were able to reach the gates to the Dwarven throne, they were to over-extended to muster anything more than a bloody stalemate right at the gates. With no side gaining any ground for the men they sacrificed, a peace was negotiated where the mountain and a small portion of the neighboring woods would be left alone, in exchange for the Dwarves agreement to not expand beyond the territory they were granted.

Arcadian Rule, Day-To-Day Life, And Culture
With victory achieved, and with nearly the entire realm under their control, the Arcadians began to establish their rule, implementing a caste that ran down from the Elves and Humans, to the Gnomes and Halfings as a reward for their early surrender, to the Dragonborns and Tieflings for their laughable failure to stand in their way, all the way down to the Dwarves for having the audacity to put a stop to their complete domination. This caste was heavily enforced socially, with those who had any reservation about the lesser's treatment being ostracized.

Magic is a regular part of the Arcadians life, with no restrictions to its practice and everyone expected to be able to wield it, to the point where the inability to do so is taken as a sign of mental retardation. While everyone had the typically expected, utilitarian spells to make their day-to-day lives easier, there was absolutely nothing stopping citizens from wielding more destructive spells, or spells that would typically be controversial to other civilizations.

The ruling body is governed by a council of 5 elected officials, who have the option to remain in office as long as they wish so long as the public perpetually voted them back into office. Each had equal say in all matters, though seniority was given to the official who has stayed the longest in office. When it came time to decide on what needed to be decided on, each will publicly announce their vote in order of least to most senior, though an exception would be made if one of them is particularly qualified in its discussion, in which case they would vote last.

Eldrazi Invasion
The Eldrazi came from out of nowhere, immediately descending onto the capital. The Arcadians had no warning, and were caught off guard with no plan besides swarming them with there own forces, including their special Battle Mages forces they were building for a second invasion on the Dwarves. They were no match as their army was eradicated by the scourge. The Arcadian's fate is currently unknown, though the prognosis is not positive.