In a fantasy setting, an explanation for different varieties of elves wouldn't need to be very elaborate, though (lots of settings have used half-elves, etc). Divinity 2 had a species created from elves mixed with dragons, then eventually corrupted by the effects of a necromancer tainting the magic in the area.
Oh, that's what they were. I completely missed the "mixed with dragons" bit, or rather I forgot: yay for having a completely ineffectual memory. For some reason I'd remembered it as elves in general being corrupted and what we were seeing here was nearer the start of the process.
I also didn't know what was the deal with the klingons, other than Worf's typically gruff "we do not like to talk about it".
