- Drows aren't evil or twisted; their society is harsh but it's not that much harsher than, say, certain human societies. Drows are simply the only elvenkind that wanted to stand up against human expansion and still, to this day, refuse to commerce with them. Their xenophobia towards humans is definitely a negative trait, but at least it has a reason.... and even if they have nightvision and do worship darkness like humans might worship sunlight, turns out that liking darkness because you see in the dark and grow food in the dark, does not mean you're evil.
This is a good idea in my opinion: play on the usual trope, pick a race (i.e. drow) or a category(i.e necromancer) that the players expect for sure will have certain negative connotations, and make them discover it was all a mixture of political propaganda and social misunderstandings. It really gives food for thought.
- Duergars are all mentally unstable..... by breed. When I read that duergar were a certain way because of how the illithid kept them, my first thought was..... pugs. They're supposed to be wolflike creatures, but we bred them into those deformed things full of congenital health problems. Surely the illithid did the same with those dwarves, especially with their brains. In fact, I think they pretty much imply this in the official manuals, but often the whole thing is not played as mental illness but only as them being "like dwarves except evil". Instead, my duergar npcs all have some form of schizophrenia. But in most of them it's not all that obvious. This is double fun when you find out drows are actually kinda good people, and then you expect duergars being evil is just another stereotype.... well, they aren't evil per se, that much is true.
- Beholders! Ok, ok, when you hear about my idea for beholders, you'll find out it's nothing particularly unusual. But then you wonder why nobody designs beholder like that. Much like the illithid, beholders are alienlike creatures who probably come from another planet or dimension. Ok, that much is a given. But for the one beholder I created so far (the patron of a warlock p.c. I have), I simply imagined a superior intelligence who sees us like we see some simple animals, and treats us like we treat simple animals. That is already absolutely horrifying. Even some of the most goodhearted people who love their cat/dog and spoil them, end up neutering them like it's no biggie. But we never imagine us in their place. "It's only an animal, it doesn't realize it's been neutered, or it's kept alone when I'm away all day.....". And that's the kindest example I can think of. As a side note, my idea of beholders is more like undescripted masses of flesh who reproduce by spores. I took inspiration by unicellular organisms. Except they're smart!