Vættir or wights are nature spirits in the Norse religion. These nature spirits divide up into 'families', including the Álfar (elves), Dvergar (dwarves), Jötnar (giants), and even gods, the Æsir and Vanir, who are understood to be prominent families among them. The term 'families' (ættir) is often translated as 'clans' or 'races'. These families sometimes intermarried with each other, and sometimes with humans.
By extension, the dead are grouped among the families of Vættir, especially when understood as being in the Underworld (Hel). For example, in the Poetic Edda, the poem Alvíssmál alternates among the 'worlds' (heimar) of the Æsir, Vanir, Álfar, Dverger, Jötnar, plus the Náir or 'corpses' in Hel. In addition, the world of humans as a family is also counted among these worlds.
The Old Norse term vættir and its English cognate wights literally mean 'beings' and relate etymologically to other forms of the verb to be, like was and were. Vættir and wights normally refer to supernatural 'beings', especially landvættir (land spirits), but can refer to any creature.
Landvættir (land spirits) are chthonic guardians of specific grounds, such as wild places or farms. When Norse seafarers approached land, they reportedly removed their carved dragon heads from the bows of their longships, so as not to frighten and thus provoke the landvættir to attack, thereby incur bad luck from them. Icelandic culture continues to celebrate the supernatural protection over the island, and four landvættr can still be seen in the Icelandic coat-of-arms: a troll-bull, troll-eagle, dragon, and handsome giant. The troll-animals are actually Jötnar who shapeshifted into the form (and mentality) of an animal, and such animals are supernaturally strong. Even the dragon is generally a troll-snake: compare the Jötunn Loki whose children include a wolf, a serpent, and a horse.
Sjövættir (sea spirits) are guardians of the specific waters.
In the Late Viking Age, Nordic kingdoms began converting to Christianity. Non-biblical Christian concepts of nature spirits, especially the German conflation of dwarves and elves and French concept fairyfolk (Old French fae), increasingly influenced the Norse concept of nature spirits. Generally speaking, from about the 13th-century onward, the Norse Vættir shrink in size. A titanic Jötunn diminutizes into a large Troll, and a human-sized Álfr into fairy-like knee-high Nisse. While the Trollir tend to represent the spirits of wild locales and the Nisser the spirits of human settlements, they overlap greatly. Both groups acquire traits of earlier Dvergar. For example, some Trollir die in sunlight and turn to stone, like Dvergar, and some Nisse make magic items, like Dvergar. Like the dwarves, elves, and faries of Christian continental Europe, the Scandinavian Vættir become accused of kidnapping human infants while leaving themselves, being small sized, in their place.
Christian concepts influenced Norse concepts but Scandinavian animistic beliefs remain strong. In modern Iceland, work crews building new roads sometimes divert the road around particular boulders which are thought to be the homes of Huldrafólk. People continue to report sightings of Trollir, Álfafólk, seaserpents, and so on, in a way similar to sightings of ghosts and UFOs in other Western cultures.
Scandinavian folklore features a class of beings similar to the Old Norse landvættir. They are known by many names, although the most common are vättar in southern Sweden (singular: vätte), vittra in northern Sweden and huldrefolk in Norway (though it should be noted that the singular vittra and huldra, respectively, refer to a solitary and quite different being). The Norwegian vetter is used much in the same way as the Old Norse vættir, whereas the corresponding word in Swedish or Danish is väsen or væsen (being), also akin to was and were.
Many aspects of the dwarves (dvergar) in Norse mythology lived on in the Scandinavian belief in vættir. They were thought to be similar in appearance to humans, even strikingly beautiful, but smaller, often clad in grey and living underground. Therefore, they were also called de underjordiske (the subterranean ones). The cautious peasant in old Scandinavia should always warn the vættir before spilling hot water on the ground, or else grave retribution, such as disease, accidents or killed livestock, was to be expected. Vættir had their own minute cattle, from which they nevertheless got a tremendous amount of milk. They were also described as having the ability go invisible from human sight whenever they wished to, as well as transform into animals (toads being a disguise of choice). This made them hard to observe, save brief glimpses; children, however, were thought to be much more capable to see through the magic of the wights.
The tomte or nisse is a solitary vätte, living on the farmstead. He is usually benevolent and helpful, which can not be said about a mischievous illvätte. However he can cause a lot of damage if he is angry, such as killing livestock.
The stories about the Norwegian huldrefolk have taken on many aspects usually associated with trolls in southern Sweden and Denmark. For example, the women of the huldrefolk were said to be quite beautiful, with the one exception being their long cow-like tails. She was in Swedish called the "skogsrå" (forest troll or spirit (from råda, to rule) or "vittra", who could also perhaps have a foxtail). They take great pains to hide these tails so as not to be detected for what they are. They are also often described as having a back like a hollow log. The Huldra often attempted to seduce men in the forest or mountains. Moreover, the huldrefolk sometimes kidnapped infants and replaced them with their own ugly huldrebarn (see changeling).
Vættir in faroes is little people living inside rocks, scared of people.