The Nótt Álfur (ノートアールヴ) or Night Elf, referred also as Yamiyomazoku (闇妖魔族) in Japanese, is one of the elf races that live in Álfheimr. But, while they have long ears and are physically similar to the other Álfur, the Nótt Álfur have a brown skin.
They are not originally native to Álfheimr. Like the Maður, they come from another realm, Svartálfaheimr, which was accessible only through Yggdrasill. When it lost its power, many Nótt Álfur were left stranded in Álfheimr. Due to this situation, the other Álfur who were once respectful of them, started to treat them as inferiors and often tried to enslave them. These, coupled with the belligerent attitude of the Nótt Álfur, led to several disputes with other Álfur and within themselves for many years. It wasn't until King Sveinn unified the several tribes of Nótt Álfur into a single country that peace was finally reached.
The child of a Nótt Álfur with other type of Álfur mostly resulted in a "mottled child" (まだら子, madarako), Nótt Álfur that either had a lighter tone of skin or noticeable white spots in the skin (often in a certain pattern). These mixed children were reviled by both Nótt Álfur and the other Álfur, so they were mostly used as slaves and were considered the bottom layer of society. Both Cú and Críe are these type of Nótt Álfur.
The Nótt Álfur in general have an inclination for belligerent actions, in particular the men. As a result, it took King Sveinn several years to unify them into a single kingdom.
"Nótt Álfur" means ancient "Night Elf" in Icelandic.