In CD10 all different manner of creatures are defined as Species. Most RPGs use "Race" instead, but considering it's a bit of a loaded word and not always scientifically correct, we stick to species for our system. Feel free to use whatever fits you the best. Take note that this article assumes that you want to adapt a playable species to CD10. For monsters, beasts and adversarial species, please see Adapting Monsters.
Definition of a species
A species in CD10 is nothing more than a collection of traits that a character from that species will begin with. There are no feats, abilities or skills that come from picking a species, as this is purely biological. That's why many traits will be in the 1-2 range as well, since they are minor variations in mental makeup from the norm, not huge, massive differences as those are more individual. Physical traits tend to vary more as those are even more genetically bound than mental traits.
Add up to zero
The thing that is common to all species, even custom, home-brew ones, is that when added together, all the traits of a species should add up to 0. This simplifies character creation and keeps species roughly balanced out towards one another. This is the default state, and unless there's a very good reason, you should stick to it for your custom species that you're trying to convert to CD10.
What defines the species?
When adapting a species to this system, you need to think about what makes that species stand out from the others and by that we don't mean what abilities they get, but how are they different from one another? What separates a human from an elf? Or a dwarf? It's usually easiest to start laying out the physical traits first, defining things like general size, affinity for one physical task or another and unique abilities such as fangs, wings, claws and whatnot. Unique traits as better dark vision, endurance etc are also considered physical traits. Remember to also consider their weaknesses!
However, where most species will vary the most is in the mental traits. This is something very often overlooked in RPGs, as players are more interested in what physical feats the species has. Mental traits play a very large part of defining a species in CD10, so take some time to really dig into what makes this species different, mentally, from others. Try to avoid things like "intelligent", "cunning" or other such pure "stat"-related descriptors and try to think more diversly. Some species are inherently more curious than others, some are born with a strong group-think, based on evolution, others are loners and suspicious of others. Some are naturally more charismatic, others more stiff.
Unique racial feats and abilities
If you're using a system that awards unique spells, abilities or skills on a species level, consider if you can change that to be a cultural thing without breaking the worldbuilding. Generally, skills and feats are things we learn in life from experience or culture, not something we are born with. However, if your system does have racial bonuses in the shape of feats or skills, you should add those to the starting traits as well. It can be as simple as just adding a new header in there, calling it "Racial abilities" and adding "Thaumaturgy" or whatever to the list.
One such example is how fay are treated in the official CD10 setting of Dark Shadows. The main civilisation, made up of three species, called "the Kykr", cannot use magic in any way, shape or form. Magic is not something native to the world of Dunia, in which they live. The fay, however, are descendents of species from a different world entirely, and function under different parameters and can access the cross-dimensional energies of their homeworld Feneira and thus use it to perform magical feats in the world of Dunia. This manifests in a trait called Fay-blooded.
This is one way to grant species-specific abilities to a species in CD10. Ideally, it should be that "this species can use magic at all" as opposed to granting a species specific skills or stat boosts.