The Peculiar Case of Birth
In world populated by many species you would expect that they would either not be able to breed with one another, or if they could you would end up with very mixed and watered out species, eventually producing a single, mixed species. However in Dunia this is not the case.
No mixed species
Nature, the gods or the grand creator, whoever was responsible for the creation of this world seemed to have had a plan. Somewhere in history, when some of the sapient species began forming an alliance and living among one another, some deity or greater being enacted rules for the world.
From that day, back in the mists of history, the three sapient species, collectively known as Kykr, of the world is capable of mating and producing offspring with each other. But instead of producing a mixed species, the offspring will be either fully one or the other, while still taking on traits from its parents. An unusually tall father might pass on his height to the child, even if the child is a different species altogether. This does not apply to any other species in the world, as far is known. In fact, the fay and Kykr are able to have mixed offspring, called fay-blooded.
Cultural and social significance
This is natural and expected to the species of the world and interspecies relationships are commonplace, as species is a concept almost completely out of people's minds. Sure they can see that the person is a different species and know what differences there are, but it's such a small factor in judging another person that it is largely overlooked. However, it does exasperate the inherent xenophobia and aggression the Kykr hold towards everyone else. They see themselves as the crown of evolution and as the natural rulers of the world. Everyone else is beneath them, such as the Dru'un Tribes, the fay, the hessak and others.
There are obviously preferences. Perhaps a person prefers illim for their crystal growths, despite being vindral, or perhaps a kuna prefers other kuna for their charming ears. It is up to the individual what their preferences are. In some parts of the world, especially among the young, it's even considered "boring" and "unimaginative" to be attracted to one's own species. There's of course nothing stopping them from doing it, but they might get teased by their peers.
In other parts, particularly where the Wolf Cult is strong, it may be the other way around. In those areas it might be a social expectation to "stick with your own".
This obviously has some rather far reaching results when it comes to evolution. Each species evolves isolated from the others, rather than taking on genetic traits from the others. But at the same time, they do slightly affect each other as some traits are indeed passed from parent to child, regardless of species. But strong species markers appear to be exempt from this transfer, such as kuna fur, illim crystal growths, illim skin change, vindral ears and blue eyes. A child will fully be one species or the other, but still you can see the resemblance of their parents in how they look. They might have "their mother's eyes" even if their mother is a completely different species, and they might share hair color with their father, or have similar cheek bones. It's a very peculiar way how nature, or some unseen power, have set this up and chooses what traits that gets passed on and not.
Many scholars, primarly Kfandrian, have speculated that because of the existence of fay-blooded crossbreeds, the separation of species is between the ancient ancestors of the fay and the sifir. They postulate that all species are descendent from either the ancient fay or the sifir, and that's where the split happened. However, that does not account for why the vindral are incapable of having mixed offspring with the other Kykr. This is accounted for by the vindral's exile on a sort of social level, but the gods must have interfered there, since their exile from the fay homelands would not account for such a drastic biological change.
The Illim are a strong, sturdy and curious species of humanoids. Honest, loyal and reliable, the illim were one of the foundational species of the Trifolk Alliance.
The kuna are one of the founding species of the Trifolk Alliance and are a canine-like species who are playful and always enjoy a good laugh.
The vindral are a minute, fay-like species belonging to the Trifolk Alliance and the Kykr culture. They are most known for their emotional detachment, sharp intellect and great ambition.
An extremely aggressive and territorial species of animal-men, gathered up under one word: The Dru'un.
The primitive Hessak, a lizardfolk living on the southern islands and particularly on Simue.