I think great points were brought up here, and thought I’d put in a couple cents.
I’d rather see so-called minority/diverse characters be individuals. This may come from being a mixed-ethnic (not biracial) woman, but I really. Don’t. Care. For. Race. I want to read about people, not groups. From what I noticed growing up, individuals often behave differently when in mixed settings versus more homogenous. And a second-gen immigrant tends (again, me looking at friends over the years, not universal) to have a different understanding of ethnicity than the immigrating generation. It continues to change as time goes by, and differs amidst individuals within that generation. There’s so many factors and all kinds of things that influence how individuals behave and make decisions. You’re going to find, generally speaking, more diversity within a group than between groups. How much research should one do to accurately portray that? I’d rather read about a character who has dark skin, instead of a character whose identity is that dark skin. Don’t get me started on how we’re to know what qualifies as “dark,” because oh, all the shades melanin and other things can do for a skintone.
I second an earlier respondent’s idea of viewing foreign films, with the caveat that you understand these are entertainment in/for/of that depicted culture, not typically documentary. 😀
So here’s my shorter reply to the question of your character being in a fantasy setting. Darker skin usually implies that ancestors were exposed to warmer climates, or more solar exposure. So really, that character, either distantly or proximately, came from a location closer to an equatorial belt. Do you need to map this character on to an ethnicity from our world? Are certain traits/characteristics really exclusive to ethnicity, or do we associate such things strongly to specific ethnicities? The advice a former mentor gave me when I freaked out about portraying my characters was something close to this, “If ethnicity is important to the plot, then bring it up. If not, then it’s not as major of a specific detail for a character within the story.” I’m paraphrasing, but I hope that may be helpful. Well-wishes and good tidings for you~ <3
+ His mercy in your dark.