When considering population, we should include land features in our thoughts. Dwarves are unlikely to be present in high numbers when there are no hills or mountains. The same is true of elves and forests. The form of government can also inhibit an entire species (or cultures within the species) from living somewhere if too much ideological separation exists between species and government. A territory may include land features that house undesirable species (and monsters), which in turn might cause repeated efforts to keep them at bay. The result will be armed forces who specialize in dealing with them, and possibly a famous hero for our world.
Our sovereign power’s population determines much of what life is like, partly because they’ll decide the form of government. Or at least, the population around at the time will. We can look to the United States as an example, for with white men in power at the time of the country’s creation, life has favored them ever since. The increasing introduction of other races has led to racial tension. While many believe other residents should be afforded the same rights, and these were intended by the founding fathers, this wasn’t the case. New laws had to be enacted and other races and women are still trying to catch up hundreds of years later.
We can leverage such a situation. Decide who founded our invented power. This will be whoever we want to dominate it. Keep in mind that a power has a capital somewhere, and within the power’s territory will be other settlements. As discussed in “Creating a Species: Habitat” from Creating Life (The Art of World Building, #1) (italics), more than one species likely created our places. There’s a tendency to decide humans built everything and all other species are bit players on that human stage. These locations can be dominated by another species instead.
We should decide what percentage of each species filled our sovereign power when it was formed, and what that proportion is today. And we should consider whether the percentage of any species rivaled or surpassed that of humanity. If the territory is half elven, that suggests they are present in many settlements (as at least a strong minority). In turn, they are prominent enough to insist on a form of government that takes into account their world view. By contrast, if they are only rarely seen outside their forests, they won’t have a voice. Minorities are always excluded in some way, even in the most benevolent society.
Since government forms change in time, this means that a power could collapse and rebuild more than once. Earliest forms of government might not have considered the elves, for example, but a thousand years and several government types later, maybe now the elves are so numerous that they impact the current government type. There could be prejudice against this or not, but it gives us a realistic viewpoint into how a sovereign power can be more equal about who’s in power.
Are there species that aren’t allowed in our sovereign power or are suppressed, openly or not? We’ll need a good reason, such as hostility, distrust, or other problems they might cause, like spreading disease. If a nefarious species is frowned upon, they might still be present. Sovereign powers cover much territory that cannot be completely policed, even with technology or magic designed to do so (nothing is perfect). Decide where in our land this unwelcome species tends to be, and how they reach that point. Do they land there (whether via ships or wings)? Maybe they can burrow to reach it. A spell or portal can put them there.
Why does an excluded species want to be here? They might be hunting animals or species for sport or food, whether there’s a famine where they live or not. They may covet a resource. They could be spying for later conquest. A benevolent species might come to spread its ideology or help people.
We might have sympathizers to the excluded species in our sovereign power. These can be people who want to overthrow the government. Perhaps they want to use these excluded species to help despite the risk. This might’ve happened in the past, too, and can be one way to create history and a fallen government long gone. The result of this can be an influx of the species and whatever good or ill they bring with them. It isn’t just evil species that might be excluded, but the good ones during a benevolent power.
We might consider the price these species pay for being caught. Imprisonment, torture, forced servitude, and death are the more extreme options.
Most of us have little idea how many people are within a geographic area. Rather than citing hard numbers, percentages can be more useful while also freeing us from unrealistic statements. Numbers might be needed when stating how large an army is, for example, but this can be easily bypassed with descriptions of how a sea of troops spread farther into the horizon than could be seen. This is more useful than a number, for it describes the impact or impression a force creates; a number tells the audience little.