Is our species good, evil, or more complicated? Our intended use of them will help in subsequent decisions.
Something violent, uncivilized, and uneducated may not be welcomed in society. Maybe the idea of them is used to frighten children into behaving. They’re a danger for travelers, especially non-warriors. Characters might have relatives injured, killed, or even eaten by this species. People go missing, in the wilderness or in space, whether there’s a gruesome crime scene or no sign of the body. Its presence causes caravans to be armed and scouting patrols to be around the community’s borders. Settlement or space station defenses will take their abilities into consideration when arranging armed forces. Weapons might be designed with them in mind. People can be skilled in tracking and scouting for them. The species will have a reputation that affects the lives of those they threaten.
A pleasant, communicative, and benevolent species will be welcomed by other societies, though possibly with reservations. They could be bringing supplies only they have access to, like plants, gems, or special weapons and armor of their creation. They may exchange information on recent activities by obnoxious species. Our characters might have friends in that species, who could’ve saved, trained, or befriended a relative. Maybe people aspire to be like them.
The caveat here is the human model—we can’t be predicted to be nefarious or benevolent as a whole. Some like to believe mankind is basically good, and while not getting all philosophical about it, this obviously doesn’t mean we don’t do horrible things to each other and even animals, plants, and the Earth. Is our new species more predictable than us or equally complex?
If they have a uniform disposition, is there a reason for this? Did a set of gods with the same disposition create them? If evil gods created ogres, maybe that explains their attitude. Were they the result of an accident that influenced them? Did they result from breeding sentient life with animals or monsters? Did someone evil or good create them and use magic or something else to ensure their disposition? How strong is that disposition? If they were created ten thousand years ago and something situational at the time made them evil, hasn’t that situation likely passed and maybe now they’re different, less extreme? Or is it perpetual and they’re even more upset?
An evil species might be less useful if shunned by society, effectively relegating them to a smarter monster out in the woods. This places creative limits on us that might be undesirable, particularly if we intend to use our setting for many stories. That species can’t do things inside a city without sneaking in, for example, but how many times do we want to use them that way before they become a predictable caricature of themselves? This can be solved by creating two races of similar appearance but with opposing dispositions, such as elves and drow (dark elves).
This can greatly extend the reach of a uniformly good or evil species, allowing new uses for them. It also creates a problem for those on our world: does the person we’re looking at belong to the good one or the evil one? Can the person standing before them be trusted? Using elves and drow as an example, the first all good, the second all evil, elves would be trusted, but now people know that drow exist. A drow could pretend to be an elf to gain access to somewhere or something. An elf could pretend to be a drow to infiltrate somewhere under drow control. If you like this idea but also like races that can be physically distinguished from others in the species, just create additional races: one that looks different and one that doesn’t; for example, elves and drow looking the same, and a third kind of elf that looks different from both.