: Actually, he was very nice to them. It was the Dwarves who refused to cooperate, but Thranduil later became their ally and friend.

: The closest equivalent to "Dark Elves" as in "Evil Elves" would have to be the Feanorians of the First Age, who willfully engaged in evil acts (the three Kin-slayings being the most
well-known examples). However, as Martin points out, there are no truly evil or inherently evil Elves in Tolkien (as the D&D Drow are).

: In Tolkien, Evil is achieved through personal choice or when free will is suppressed by a greater will (as with Morgoth and Sauron the way they dominate their servants).

I expected someone to mention Eol (sp?) Wasn't he called a "Dark" Elf? As in "hadn't heeded the summons to the light of Valinor". It's been a long time since I read it but there's some guy - Elf I'm pretty sure - who was featured in the fall of Gondolin story of the Silmarillion. Was he a rival to Tuor? or Earendil? I remember something about him being "bad-hearted" keeping a lady prisoner in hiis woodland home. Wow I really can only remember bits. But someone must know what I'm talking about.
Anyway - I don't think this is what the original poster meant by the question and it's certainly true what M. Martinez said about free will in Tolkien's world.
Can anyone enlighten me?