The Moriquendi (singular Moriquendë: also named the Lembi, Hisildi, and Kaliondi) were the Elves of Darkness: those who did not join the Great Journey over the sea and behold the light of the Two Trees in Valinor. They lingered on the shores of Middle-earth or, indeed, never passed the Blue Mountain in the east of Beleriand or the Misty Mountains further to the east. Those Moriquendi who originally started on the journey but did not finish it were named the Úmanyar, which meant "Those not of Aman".
Moriquendi is a term for elves of the Avari, Sindar, and Nandor, but in practice is only applied to the Avari. An exception to the hierarchy of Elvish peoples is Thingol, who, though he did not complete the journey, had earlier been to Valinor. Thingol was therefore considered Úmanyar but not Moriquendë.
- "Those Elves the Calaquendi call the Úmanyar, since they came never to the land of Aman and the Blessed Realm; but the Úmanyar and the Avari alike they call the Moriquendi, Elves of the Darkness, for they never beheld the Light that was before the Sun and Moon." -- The Silmarillion, chapter 3: Of the Coming of the Elves and the Captivity of Melkor
The term "Dark Elf" in Tolkien's writing seems to hold an additional special and not explained meaning, as it is given as a special title of Eöl, and Elf of Nan Elmoth. It is also used as an insult by the sons of Fëanor to Thingol (which is incorrect, since Thingol alone of the Sindar was reckoned under the Calaquendi).
- The Silmarillion: Quenta Silmarillion
- The History of Middle-earth, Vol. I: The Book of Lost Tales Part One: Index
- The History of Middle-earth, Vol. XI: The War of the Jewels: Part 4, Index