“Black skinned elves are for killing.”
There is an absolute limit to the number of race/culture combinations that a game world can handle, which is essentially unmodified whether there are large numbers of races or small numbers. That is, when detailing the continent, you will write up a series of different cultures until you run out of space on the map, run out of word count, run out of allotted time for world building, or are for some other reason required to stop. Whether the new group of shark cultists is an entire species of people who are so small in number that all of them in the world are members of a single tribe that happens to worship a shark, or merely a tribe of shark worshipers from one of the races previously defined is unimportant to how much writing time, word count, physical space, and conceptual space they take up during the world building exercise.
And so it comes back to a question of whether fantasy races are needed at all. If a race of scaled humanoids is not actually needed to put in the village of shark worshipers that are called for, why bother having a race of scaled humanoids at all? There isn't really an answer for that, but on some level people genuinely want there to be people from other species, even if when it comes down to the wire every single species you could name is completely expendable. So it comes that the number of races that are to be included in any world is actually completely arbitrary. Each race unnecessary, yet hopefully still cool enough as a setting piece to justify the believability their very presence damages in the reader.
Mules
“Would you have sex with an owl? Maybe make some kind of half-owl?”
Members of two different species can't make viable offspring between them with sex. That's what being a different species means. Any setting where there are half-orcs and half-elves is one in which by definition the orcs and elves are just kinds of humans, not really different (and certainly not importantly so) from other humans. And while that is certainly a kind of fantasy – one in which you can have sex with exotic slant eyed beauties with gracile frames – that's actually completely achievable just by going to Nippon and does not require the invocation of the otherworldly in any way.
Any race different enough to be called that should be infertile with humans and every other distinct race. This doesn't mean that you can't rub your penis on orcish ladies – it just means that you can't father any children while doing that. If you want exotic women with strange customs, different looks, foreign languages, and distinct skills with which to make a half caste child, you are more than welcome to go down to the villages of the Water Benders. They have differences in everything from their magic to their skin tone and yet they are still entirely human in every way that counts.
Humans
“See these thumbs? See them!?”
Humans are actually not very different one from another, and it is unreasonable to think that humanity will be especially more varied than any other particular sapient race. They often get put into the “variable” slot because authors are lazy as fuck – and since humans are the baseline of our experience anyway it's difficult to imagine humans as anything other than the blank slate upon which all others are written. But honestly that's very much not what humanity is all about. Every human's capabilities are pretty much interchangeable and the genetic variations are minuscule. Humanity is a young species that has gone through a relatively recent genetic bottleneck and our strengths and weaknesses are more normalized than almost any other animal. If there are other races in the world, especially if they are older than humanity (as common a trope in fantasy as can be found), it is reasonable to believe that they would be more varied physically than us. Indeed, humanity is virtually at the limit of sameness one member to another that a species can attain without being wiped from the world in a handful of generations.
Which is not to say that humans are a weak species. We are actually kind of cool. We learn languages super fast, we teach techniques to each other quickly and easily, we are inherently curious and experimental, and we individually have crazy lots of endurance. This mans that we can push our people all over the world and develop workable lifestyles for diverse environments and then pass those lifestyles on to our kids. Cultural diversity looms fairly large in humanity, because that's what humans do.
In a magical world, knowledge of language combines well with curiosity and experimentation in order to produce – not science – but magic. Humans were the first animal in our world to metal working, and in a magical world metal working is done with sorcery. So humans are very good at sorcery. And they can walk long distances and carry relatively large amounts of goods for long distances. The human is not a true omnislot, it's a member of an up and coming race of high endurance creatures who have developed a lot of magical techniques in a short period of time.
That is humanity in a world where magic works and other races exist.
Orcs
“Waaagh!”
The idea of a race which is more “savage” than humans are of course has a lot of traction. It's something to be afraid of and also to feel superior to, and I don't think that needs a whole lot of explanation. But racially speaking, a sapient race is not “savage” or “civilized” except as a group. And even then we're talking about individual tribal groups rather than racial collectivism. For every Isaac Newton you care to name, there's a Timur the Lame out there to make you feel bad about your species all anew.
That being said, our closest living relatives on Earth are indeed pretty well described as being savage. The Chimp is named pan troglodyte by scientists and they are not kidding. They have stronger musculature (but less endurance), have a more difficult time with communication, inherently rely on themselves more and help one another less, and are both easier to offend and more likely to fight than flee when startled. The chimpanzee thusly manages to take its relatively small differences from a human and become something that has never developed technology more advanced than the spear. One which has developed war and trade but not agriculture or government. To my knowledge, no chimp tribe has ever changed government because of elections, but always instead by combat or betrayal.
These traits though are frankly too much for a fantasy race that is expected to be of much threat in any circumstance other than “It's jumping at you out of a tree, what the blargh!” which of course is also a circumstance in which leopards and jaguars have been terrorizing humanity for millennia. For a race to be really meaningful in a magical world they have to be making some of that magic. Magic of sword making. Making of setting shit on fire. Magic of killing fools in their sleep. That sort of thing.
The less technically competent hominids were all still hominids. They imitated well. Even when the Neanderthals went a hundred thousand years without seemingly changing their construction techniques or creating different material culture (at least, of that material culture which survived the eons to be found by our archaeologists), they still adopted any technical developments that humans showed up with quickly enough that it doesn't even show up as time in the archaeological record. And so it is that a race of monstrous humanoids would still be capable of using any magic and any tool that they were exposed to if they were to be called humanoids at all.
So what do the orcs do? Well, first of all they've been around longer than humans have. Secondly, they are physically stronger than humans are. They have sharp teeth and are therefore carnivores, complete with having the shorter intestinal system that carnivores are saddled with. They have less endurance and less patience than humans do. Backstory wise, this means that they came up with a lot of simple magics long before humans even existed, but that their more complicated magics were invented by humans and then the orcs learned them from teachers.
Culturally? Whatever they want to do. Orcs still have children and parents and language and knowledge and so on and so forth. Their biological demands make civilization very different for orcs than for humans, because they don't benefit from agriculture directly. They literally had to skip the entire period of human agriculture where we lived on grain and onions, because they can't do that. Those orcish societies which have taken to living in cities surrounded by fields have to have done so after humans did because it requires an extra step for them. A field of oats is of no use to the orcs unless they then take those oats to a feed lot and grow some other kind of animal on it and then eat them. While an urban environment can sustain a huntable population of pigeons and rats for a carnivore to eat, the number of such carnivores can't be very large. Indeed, most areas can't contain very many carnivores before they run out of food. So most orcish societies are either based on very small numbers, or larger groups that move around a lot. The advent of stable cities that use agricultural techniques to create large amounts of food for stationary herds is incredibly new, an adaptation of human techniques, and presumably highly controversial. Orcs never had a conflict between Horus and Set (nor the blatant rip-off story of Cain and Abel), because orcs never had an agricultural option. The historical orcish dilemma is between pastoralist nomads who domesticate animals and hunters who don't. They also have a secondary historical dilemma between smaller groups who stay in one place (and either hunt and fish or keep herds) and larger groups that wander around (either taking their herds with them or eating whatever happens to live there).
So you can see why orcish traditionalists might be pretty offended with the new innovation of making a really big city, having orcs grow food crops, taking the food crops back to domesticated animals, and moving on. That's appalling to many orcs who frankly aren't used to doing much work. And orcs are generally a fairly spiritual people because they don't have very much patience.
- Indian Flavor: The Rakshasa are essentially orcs. They have sharp teeth, they eat meat, they are strong, they hit things and so on. Rakshasa do not all have tiger heads, that's just a thing that some of them do. Little details like having black oily blood and thumbs on the other side of the hand are certainly cool, but can honestly be shifted back into the orcs in a European setting because they are cool.
“These woods are ours.”
There is a persistent need in fantasy stories for having races that are made out of magic. The elves, brownies, nisse, tomte, alfar, goblins, ouphe, dwarfs, kappa, and what have you are in fact all essentially the exact same fucking thing. And thus it is exceedingly unhelpful to attempt to treat them as being any different one from another. The extreme example of course is the Drow and the Derro of D&D – those two words are pronounced the same way because they are the same word for the same creatures from the same folk stories – just transliterated differently because medieval people in Northern Europe can't spell. But once you've determined that you do in fact have a race of people smaller than humans who are mysterious and made of magic – so what? It's a magical world, everything that you can do that other people can't do is by definition magic.
A magical race is magical because they can do a lot of things that they can't teach you how to do. In short, they are magical not because they have great wisdom, but because they don't know how they do things. Elves therefore are at the very least inarticulate, and quite possibly instinctually compelled. This is a dangerous road to go down, because of course if a creature acts too much by instinct and not enough by learned behavior it is in fact not a sapient race and therefore not worth talking to and barely worth talking about. So stepping back from that particular precipice, we can have creatures who template themselves on their environment severely as they grow – like how alligators develop sexually based on temperatures only more so.
This ties nicely into a lot of the elven folklore, where for example nymphs get all kinds of traits from the streams of their homes while oreads get mountainous traits and so on and so forth. An alfar raised in any environment will simply imprint on that environment and get abilities and features related to that area. Even though he can talk, he can't tell you how to do the things that he does any more than a human can tell you how to digest grain. And that makes the alfar magical to the people living in the setting. Every alfar has secrets that literally cannot be shared.
Alfar culture is of course highly fragmented. The snow dwelling Frostlings can certainly interbreed with the Mountain Dwarfs because they are the same species, but they don't really have much to say to one another. They don't look that similar (alfar natural camouflage patterns itself off of surrounding terrain at a young age), and they can't do terribly similar things. And most of all, the only way for a Frostling to teach a Mountain Dwarf any of their really cool tricks, they'd have to start with a baby Mountain Dwarf and just raise them as a Frostling – at which point the child would be a Frostling and not a Mountain Dwarf.
- Indian Flavor: The Gandharvas and Apsaras fit this role admirably. They have inherent magical powers, they come in many different shapes, and have a distinct locational affinity and varied essences and powers based on that locational aspect. Which means that the exact same description fits either way. You just call them Gandharvas instead of Alfar and move on with your life.
“A place for everything, and everything in its place.”
Let's talk about Zerg. Or really any hive oriented creatures. Mammals can and do form hives (see the mole rats), and many would say that humanity is at its most effective when it most closely approximates that lifestyle choice. Unlike science fiction B movies there is nothing innately horrifying about being a member of a hive and hive members have no special incentive to force other beings to join their hive, and even if they did that really wouldn't be a subject for cosmic horror anyway. Eusociality is merely the highest level of social organization, and for those living in it the experience is at least as comforting as patriotism or familial piety.
But nonetheless, arthropodal species of sapients hold a weird fascination for us all. They have something approximating bone on the outside, and though they would definitely need to have some sort of internal scaffold as well to achieve human-like size, that still looks both creepy and awesome. Free of the tyranny of upright posture, four limbs, and such a bug person can look like anything. In fact, with the race having a reproductive division of labor and probably a functional (rather than merely social) caste system for its members, there is no reason that every member of the species has to have the same morphology. It's a way to go ape shit with gender and caste multimorphism. Size, shape, and function can all vary wildly within different groups of the same species.
At the minimum, the hormigan species will have four castes: Drones, Workers, Soldiers, Queens. As sapients however, there is no need for there to be an established constant social order within that. It is an absolute fact that only a relatively small number of people need become mothers to spawn a new generation, and that those who will become mothers must be selected and groomed for this role years in advance. Whether these prospective mothers are imprisoned or taught bureaucracy and government during their transformation is a socially defined accident of history that will doubtless vary from hive to hive.
Physically the hormigans resemble humans the least, and so it is important to not just check every box that would make them more alien and harder to identify with. Each individual hormigan is still able to learn and speak and act on their own. The fact that society as a whole has requirements of many members to persist generation to generation does not put any constraints on the individual (unless they have been selected for motherhood, in which case it does). Whether a hormigan is a soldier with blade arms in addition to manipulative digits or a worker with chemical excretory abilities, there is really nothing to necessitate them staying in the hive and whiling away their lives without adventure.
Remember that being an individual hormigan is like being a Eunuch who is related to a government official. From an evolutionary standpoint, there is no amount of personal success that really matters if the hive does not succeed. There is no personal sacrifice which will have any real cost in two generations, and so extreme patriotism is pretty common. It is therefore reasonable to guess that hormigans developed cities and nationhood much faster than other races – indeed these things come very naturally to them.
-Username17