I read the first 7 books of R. A. Salvatore's Drizzt books (Homeland to Legacy) when I was a teenager. I loved the idea of dark elves, and especially loved the exotic look - black skin and white hair (which is part of why Storm's my favourite X-Men character). At the time, when I started planning my own fantasy novel, it never occurred to me that they might be considered 1) racist or 2) copyright of TSR (now Wizard's of the Coast). I just thought they were cool.
Skip ahead through university and I realized I not only had to explain how my protagonist became the only black elf in my fantasy world (as I decided not to do a race), but also modify the look so it wouldn't be considered plagiarism. I'd never considered using the name 'Drow', but the look for a dark elf is pretty obviously their own. The first was easy - I split my humans into light and dark skinned, depending on where they lived. As for my dark elf, I made his colouration due to a potion gone wrong, and modified the look enough that it's now my own idea. Problem solved.
Recently while shelving I came across this book: Demons Not Included by Cheyenne McCray. Apparently she also liked the idea of the Drow as she made her character a half-drow. I checked the wikipedia listing for drow to find out if Dungeons & Dragons (the basis for Forgotten Realms) had cribbed it from history and therefore it is fare game to anyone wanting to use it (like dragons, elves, etc.). Turns out the word 'drow' is of Scots origin and more commonly written 'trow' or 'troll'. It referred to 'dark spirits' or a race of elves that lived underground and were good at working metal.
Everything about them, from their look to their society, was created by Gary Gygax and Dave Arneson, who co-created Dungeons & Dragons, and later writers for the game and books.
So my question is, is it right for another author to crib off of someone else's work in a situation like this, where the creature has become part of the public consciousness for the genre? Could an author use Thestrals in their novel, which unlike many of the creatures Rowling used in Harry Potter, were original creations of hers? Or should Drow be considered intellectual property of WotC and unusable by other authors until the death +70 years rule has passed? I'd lean towards the latter myself. I think it would be annoying to spend a lot of time and effort creating something and then find others using my work as background so they don't have to do the same.
I'm interested in hearing your thoughts on this matter.