Álfheimr is mentioned in Grímnismál and Gylfaginning. The elves appear throughout the Eddas, the sagas, and later Scandinavian folk tradition. The distinction between light elves (ljósálfar) and dark elves (dökkálfar) comes primarily from Snorri, who may be imposing a Christian-influenced dualism on older, less binary material.
The Norse Elf
The Old Norse álfr (plural álfar) is not Tolkien's elf, not the Christmas elf, and not the fairy of medieval romance. The Norse elf is something older and less defined — a being of intermediate status between gods and humans, associated with light, fertility, and the kind of power that operates close to the natural world.
Snorri distinguishes light elves (ljósálfar) from dark elves (dökkálfar). Light elves are "fairer than the sun to look upon." Dark elves are "blacker than pitch." He places light elves in Álfheimr above the earth and dark elves below. This dualism is suspiciously clean for Norse mythology, which usually resists clean dualisms. Most scholars believe Snorri is imposing a learned, possibly Christian-influenced, schema on material that in older tradition did not divide so neatly.
In practice throughout the sagas and the poetry, elves appear in multiple contexts: as honored ancestors (landvættir, land-spirits, sometimes overlap with elf-concepts), as beings to whom blótar were offered (álfablót — the autumn elf sacrifice is attested in several sources, notably in the poem Austrfararvísur by Sigvatr Þórðarson), as causes of illness (elf-shot — alfshot — was the Old Norse term for unexplained internal pain, especially in animals), and as beings who could be placated or appeased through ritual attention.
The connection between elves and the dead is significant. In some saga accounts, a dead man described as particularly accomplished becomes an álfr after death — his grave mound becomes a site of offering. Óláfr Geirstaðaálfr (Olaf the Geirstad-elf) was a Norwegian king whose grave mound was offered to after his death, and who was apparently understood to have become a local protective spirit of the elf-type. The boundary between honored dead and elf is permeable.
Álfheimr and Freyr
Grímnismál states that Freyr was given Álfheimr "as a tooth-gift" — a gift given to a child at the cutting of the first tooth, which in Norse custom was a significant event. This detail is unusual: Álfheimr is not his domain of function, but a gift given to him before he was old enough to speak. The connection between the Vanir god of fertility and the realm of beings associated with fertility, light, and the agricultural cycle is not coincidental. The Norse probably understood Freyr and the light elves as operating in the same theological space.
The Álfablót
The elf-blót was one of the most private sacrificial occasions in the Norse calendar — performed at the household level, not at public assemblies. Sigvatr Þórðarson's poem describes trying to find hospitality in Sweden in autumn and being refused entry at several farmhouses because the women inside were performing the álfablót. Outsiders were not welcome. The rites were closed.
This privacy distinguishes the álfablót from the great public blótar (Yule, Dísablót, Sigrblót). Whatever happened in the elf sacrifice, it was done by the household for the household — probably for the household's dead, for the land spirits, for the protective powers that lived close to the living rather than in the distant divine courts. The elves of Álfheimr and the elves of the doorstep are connected, but the connection is not a simple identity.