Ashsilverlock has a great essay up on Fabulous Realms about The Dark Court, AKA the mythology of dark elves. An excerpt:
Dark Elves have actually been around in mythology almost as long as Elves themselves – Celtic folklore in particular is full of tales of the Dark or Unseelie Court, causing mischief and mayhem for both humans and their Light or Seelie Court counterparts. They are also referenced as Dokkalfar or Svart Alfar in the Norse myths. In the Eddas Dark Elves were not truly evil as such, they could mainly be distinguished from Lios Alfar (or ‘Light Elves’) by the fact that they dwelt within the earth and were mostly swarthy, while their cousins lived in Alfheim, located in heaven, and were said to be fairer than the sun to look at. There also seems to have been some overlap between Svart Alfar and Dwarves, although this is done away with by Tolkien in his legendarium, which refers to them as two different races. Tolkien’s Moriquendi seem to be the origin of Dark Elves in fantasy fiction because it is in them that the term ‘Dark’ is first given a specifically negative connotation. In Tolkien’s world, from the beginning there was a division between the Elves who desired the light of the Undying Lands versus Elves who did not wish to leave Middle Earth, implying that these ‘Dark’ Elves willingly tolerated the shadows that the Dark Lord Morgoth had put upon Middle Earth.
