@Leyelle, are you black or know any black people? I'm going to assume no since you're having this problem, but getting advice from your subjects is usually good advice.
Practically speaking- Find some books on the subject. Malik Shabazz (Not the hotep guy) had a very well regarded art book called How To Draw Black People some years back.
I just did a search for it on Amazon, home of undercutting the competition, but it was over $100. This suggests to me that it's out of print now. I couldn't find it on his website either. Might be worth asking your local library about it.
Personally speaking- There's skin tone and there's skin tone manipulated for media.
I'm assuming Nyakim Gatwech is the inspiration for wanting a very dark skinned character. It might help to realize that a lot of photos of her are Photoshopped to exaggerate her features, like with all models. Wikipedia has a photo of her under normal lighting conditions you might want to look at. She's lovely naturally and her skin tone is good for manipulating into something striking, but it's still manipulated and thus, unreal.
What I'm getting at is that you can have a dark-skinned character with clear features without them being, well, drow from D&D.
I now see this was covered but it bears repeating.
Unless you're making a drow, or even Mr. Popo. But those both require a far different approach.
BTW, my advice for anyone reading this post for drawing Mr. Popo is pretend you never heard of this character before and never will hear of it in the future.