Formed over 600 years ago when the many disparate warring nations of the continent of Ardora were united under a common banner through a path of careful and calculated conquest by the nation of Tenetria, the Myriad Nations functions as both a diverse mix of individual nations with their own independence and as a single unified empire.
Few restrictions or rules are imposed upon individual nations, and indeed nations rise and fall as feelings change and people break away to form their own nation where they can really be themselves, and either succeed or die trying. Nations are left to do their own thing as they please in the most part, though one of the nations is designated the Lead Nation, whose ruler acts as the Emperor of the Myriad Nations. This Emperor has the power to issue diktat which the other nations must follow. The Lead Nation is Iruspin, and the Emperor is Orei VII.
To avoid the great wars of the past one of the main restrictions in place is that invasion of another nation is illegal. It is quietly accepted that through border skirmishes the borders between lands considered of different nations are slowly redefined, but to outright attack another nation is to go against what the Myriad Nations stand for, and will typically result in an intervention by the sizeable Imperial Army. Of course, far from Iruspin, it is not unheard of for an opportunistic neighbour to just wipe out a smaller nation and claim the entirety of their land on the basis that they will be unable to get a message to the Lead Nation in time, and so there will be nothing to defend by the time it becomes relevant.
In the immediate aftermath of the Moonrise Event the Emperor issued an order for those who are in a position to do so to investigate and report back to Iruspin. Since then, the orders coming from the Lead Nation have been few and far between.
People across the Myriad Nations have not developed a consistent currency. Rather they typically operate on an economy of favours: those with a particular skill provide their services or produce for those who need it, and in return they'll do something for them, and so on, with the expectation that it all balances out in the end. Even if the farmer does not need the clothes the tailor can produce in exchange for the food she's given them, chances are she'll know a doctor who does, whom she happens to owe for some medicine provided in the previous month, and so on.
As such the people of the Myriad Nations take favours quite seriously, and by doing something which benefits another one can typically expect to be able to call in that favour at a later time.