Alfs, Disir, Valkyrie, Land Vaettir, and other Wights inhabit the "spiritual" and material Worlds. They make up the "mythology" left us in Fairy Tales and legend, yet are a vibrant and living part of reconstruction, and understanding the Universe.
The Alfs, are ancestral spirits, akin to ghosts. They are generally beneficial to mankind, especially to their clan. They usually reside in their burial mounds, funerary barrows, or some nearby natural landmarks. Frey presides over them as a God of Inhumation, and is called the Lord of the Alfs. The Light Alfs are released spirits, free willed, and essentially human in nature. Usually they take on (or are born from) male traits, and are thus the forefathers one "gives honor" to.
The Svart-Alfs are not "free", in the that they are not transcendent beings, and were never human. They only exist as "dwarves", and do not have a soul complex that allows them to exist after death. A dead dwarf brakes down into his elemental nature, and is wholly destroyed. It is said that the Alfather must make a new one to replace each departed one. While alive their sole mission is to create, for woe or weal. They forge the weapons and adornments of the Gods. In the beginning, the Edda states Odin created them from Maggots, and that they hold up the four corners of creation (Midgard). This reinforces their elemental nature, and makes them beings of Order, yet it is order without consequence of good or evil.
Like the Alfs, the Disir and Idise were ancestral spirits, but feminine in nature. They were attuned to the roles of Wyrd and were concerned with family orlog. The Disir often mediated on behalf of their living kin to the Norns, and some folk actually confused them with the Norns, calling them personal Nornir. They understand and respond to the patterns of Wyrd, and can help write around some of the Web's twists, but they always seek to maintain the harmony of Wyrd. A special group of Disir serve Freya carrying half the fallen heroes to Folkvang, another group, called Valkyrie serve Odin in the same manner, carrying them off to Valhalla where they become the Einherjar, the chosen warriors. Here they manifest the greatest function of a guardian, to ward the spirit through the passage into death.
The Land Vaettir were the sum total of the life force of an area. They embodied the strength or weakness of a tribe of people. The Vikings erected the Dragon heads on the bow of a longship to frighten enemy Land Vaettir, in turn they removed them when approaching home ports so as no to offend their friendly ones. The spiritual health of a politically united people gained consciousness in a Vaett, though certain areas had indigenous Vaetts that existed without a populace. These wights also inhabited ponds, rivers, streams, and other natural "topographies" They are related to the Huldufolk [Hidden People], who are cunning and deceptive, but possess powerful magicks. They tend to be evil, but many befriend men anyway.
Another group of Northern denizens were the Woeful Wights, the Utangards (the Out dwellers). There are many such wights, some spiritual some physical, and some beyond the two. They haunted the hills and forests, stalked travelers on the roads, and preyed upon the good folk in dark times. These creatures usually fit into one of three categories: Shape Shifters (polymorphic), Undead (reanimated), and Trolls (paranormal). However, due to the ill nature, and power of the darkness recognized by the Northern Tradition, it can be posited that these generalities may not always apply.
The Shape shifters were not all evil doers. In fact, some were definitely good. Many Spae workers (Vanic Magicians) were able to alter their physical form, frequently becoming cats or birds through utilegija (lying out). Odin's Berserkers shape changed into bears, and fought with Wod inspiration and ecstasy in a battle frenzy. But, like Loki (who shape changed into many things), there is a blurring of animalistic and darker human instincts that seem to emerge in those that polymorph.
The Ulfhurgerer, the wolf equivalent to the berserkergang, never had mastery over himself, and as a result became a menace to his own as well as the enemy. Herein begins the Werewolf legend. It seems that as time progressed, the man became lost in the wolf persona, until all that was left was the instinctive (primal) consciousness. It is likely that they became outlaws, and eventually slipped out of humanity altogether. This would explain how the werewolf became such an archetypal image of evil, for it was man in his darkest corner, removed from his light nature. This is an excellent reason for the werewolf's aversion to the sun, and the full moon, as the symbol of natural rhythm, became the catalyst for the transition. These are nonetheless physical beings. They posses Lyke (albeit altered) and Hyde (although deranged). The reason they may fear silver is its "pure" nature, "wolfs bane" was likely an original component of their spellwork, and thus brings them into cognition of their humanity.
The Undead in the Northern world are unpleasantly nasty, and given to all too physical a form. The Draugar, are the walking dead. Not all were evil, as with the shape-shifters, some brought important news to the clan (a death, an approaching disaster, or even the need for vengeance). But the fear that they inspired caused the folk at large to shrink from them. Many funerary practices were aimed at preventing these creatures from arising. The dead was never taken out a regular threshold, for that gave them invite to return to the house by the same means. A very important note, conscious evil may not enter a Tru-Stead (home) unless invited by a member of that household. Often trickery (deception, illusion, u.s.w.) or manipulation is used by an evil Wight, in an attempt to gain entry. (Even those Good-Wights often need formal invite to enter a home!) The funeral door of a house was boarded up after the body was taken out, thus sealing out the evil. Shoes were often tied together to prevent inhumed corpses from walking in death, and cremation prevented the physical Draugar (the more dangerous) from reanimating.
The dead are often endowed with extraordinary strength, though their Lyke is degenerating, it is raw Might. But they seem to have only parts of the spirit left, and seldom have consciousness or life-memories. They have lost their fetch, and in a sense, connectivity to Wyrd, and they have not the inspiration of Wod, yet the Athem lives on; they are operating outside of natural law, defying it. It is just this aberration that makes them so "scary" to the mind of man. If death is a place of rest, then the Undead disrupt the very nature of our secure conviction of our passing.
Sometimes the Draugar remember their deaths, and it drives them into after-life existence. Sometimes they live on due to enchantments, or because of a particularly evil earthly life. In any case, they are horrible creatures to encounter. A few are self made Liches; so powerful a Vitki may endow himself and retain a degree of consciousness, but sanity turns to an evil cunning, vicious and malign. They may be put to rest by powerful magick, or the correction (vengeance) of the problem that makes them walk. They are usually immune to normal weapons (though silver and iron are known to hurt them), but have an aversion to things "holy" (not in the Christian sense).
Another rare Undead is the Vampyre. Not to be confused with the legendary Vlad Dracul, this entity feeds on the life-force (symbolically blood, semen, and spittle) of men and (in dire circumstances) higher mammals. They may or may not have "died" in the traditional sense to achieve this condition, but the Undead ones are often the more evil and dangerous. Like other Outdwellers, they avoid light and holy things, magick does seem to be effective. They seem to be hypnotic, and can appear as beautiful, and seductive (a purely sexual vampirism is possible, though, it would seem to be a "psychic" form of vampirism... the true vampire would likely use those techniques as a means to their ends). It is thought they can shape change as well, and have extraordinary strength. They are fortunately few and far between. Folklore favors garlic and wooden stakes, though iron spikes, silver daggers, and decapitation may be terminal to vampires.
The last category is the Troll. While we have spoken of them in their relation to Giants, they are often something more than force. When they develop a degree of attachment to an natural feature (hill, bridge, waterfall, u.s.w.) they begin to interact with the natural world in a more tangible and structured manner. They can appear as large or small monsters, or take possession of men. They frequently carry off people for mates, and the children are half trolls, usually evil in bent, but possessors of powerful magick.