Dark elves are humanoid creatures. They specialize in a variety of dark magic and are always lurking in the darkness, they are natural assassins. The seem to communicate with a type of chirping sound.
When Ye Yan discovers the base of the Dark Guild it is in an underground crypt and there is evidence of Troglodytes and Dark Elves. After Nie Li enters the cave, he discovers that it is actually the entrance a vast underground world. this place is called the Nether Realm and many of the different races live here, including the dark elves.