Dökkálfar and Ljósálfar

In Norse mythology, Dökkálfar (Old Norse "Dark Elves", singular Dökkálfr) and Ljósálfar (Old Norse "Light Elves", singular Ljósálfr) are two contrasting types of elves; the prior dwell within the earth and are most swarthy, while the latter live in Álfheimr, and are "fairer than the sun to look at". The Dökkálfar and the Ljósálfar are attested in the Prose Edda, written in the 13th century by Snorri Sturluson, and in the late Old Norse poem Hrafnagaldr Óðins. Scholars have produced theories about the origin and implications of the dualistic concept.