Dark Elf

Dark elves are the (mostly) evil counterparts of the Light Elves (or High Elves) in many mythologies and fantasy settings. They are often at war with other elves.

Dark elves in mythology and folklore

Norse/Germanic mythology

In Norse mythology, Svartálfar ("Swartelves" or "black elves"), sometimes considered synonymous with duergar ("dwarves"), are subterranean creatures who dwell in the world of Svartálfheim. They may be either benevolent or malevolent. The original Svartalfar worked the forges on the lowest level of the world tree. These beings were not considered evil to begin with, and the Black or Dark skin was a result of working at the forge.

The Dökkálfar ("Darkelves") are male ancestral spirits who may protect the people, although some can be menacing, especially when one is rude to them. They are generally light-avoiding, though not necessarily subterranean.

Celtic mythology

In the Celtic language, the Daoi-Sith are "dark elves", while the Du-Sith are "black elves". Both terms are obscure, and the latter seems to have been used as a proper name. Apart from an ambiguous folktale of uncertain origin involving one Sir Lachlan Mor M'Clean [1], there are no known surviving myths or stories associated with these creatures in Celtic mythology, so it is impossible to tell whether they were thought to be elf-like, troll-like, or something completely different, or if they were even similar to each other, if they were good, evil, or either, etc.

While the terms exist and were apparently used for something, it is currently impossible to tell exactly what. However, it seems possible that they are related to the Drow of Scottish folklore, if not direct precursors.

British Isles folklore

In the Orkney Islands, the Trow or the black elves are similar to the Svartalfar or to Scandinavian trolls or dwarves, and inhabit mines and caves. They may be either good or evil, but the evil variety are more common.

The Drow or the dark elves are the Shetland Isle equivalent of the Trow, but unlike the trow, they are thought of as exclusively evil. They are tiny elves known for their mining and metal-working, not unlike dwarves. A useful way to envision them may be as evil, subterranean counterparts to tiny shoemaker elves.

In Irish mythology, a drow is a stone monster of the Fomori, similar to the Scandinavian troll.