In the Norse tradition, there are various types of spirits and wights. Interestingly enough, female spirits tend to get grouped into one of three categories: Disir, Fylgjur, and Valkyries. I think all three of these female spirit categories are interesting. For some reason, they all overlap each other. It gets very confusing when trying to determine what is what, exactly, due to this. In the lore, sometimes the terms are used interchangeably and sometimes they are used separately. So, this is my understanding of each category of these classifications of female spirits in the Norse tradition.
A dis ("lady") is a spirit (sometimes thought to be a lesser female deity or wight) who plays a role in the fate of a person, a persons general wellbeing and attributes such as luck, orlog, and are representative of death in other instances. The word "disir" can roughly be translated to "divine goddesses", but at the same time they are not viewed as highly as the Goddesses found in the Aesir/Vanir pantheon- rather, Disir are viewed seperately, yet still slightly above a normal wight. (Interesting fact: One of Freyja's names, Vanadis, actually mean's "Dis of the Vanir" and Skadi was once referred to as snow-shoe dis). The Norns themselves are often called Disir. Appearance wise, they are thought to look a lot like valkyries, and beautiful women in general.
Disir are intrinsically tied into familial relations and kinship. They were sometimes thought to be ancestral spirits, sometimes collective spirits of a person's family ancestors, who guarded and looked after their descendants. They play an important part of wyrd and orlog concerning the individuals that they watch over. Like any entity or deity, they have the capabilities of being good, or bad, and all the spectrums in-between. They can be friendly, loving, helpful protectors. And yet they can be merciless, hateful, hostile enemies. Throughout the sagas and tales, you get a picture of both sides of the coin- and what it means to lose the favor of a dis. One one hand: the disir provided luck, helped in childbirth, gave warnings and protected the individual/family they watched, helped them in battle and otherwise watched over the family. However: In the tales, youll find mention of disir becoming ill-tempered (whether due to a lack of sacrifice, some anger provoked by the individual or family, a dramatic or sudden loss of luck, or for no apparent reason) and this bodes ill for the person/family, sometimes resulting in the death of a person.
" ...the idises* act, not only as shapers of the family line, but as embodiments and transmitters of its orlog and the whole spiritual complex associated with it. A family, or aett, which is mighty of soul will have mighty idises who look upon its bairns with a kindly mood and give the best of gifts; but if the heritage carries an ill orlog, the idises will bring that down upon the children of the line. " (Gundarsson)
They were honored, typically at what is known as a Disablot. This is a sacrifice to the disir, normally around Autumn or whenever winter is beginning. (Winternights). This blot generally honors the Disir and the Valkyries at the same time, while also honoring female spirits and ancestors. The purpose of the blot is to bring luck, and prosperity to harvests (I've seen some Kindreds actually do this blot during the spring, though traditionally I don't believe it was done during this time). Snorri lists several examples of the disablot throughout his works.They were commonly conducted in a private household, though there have been examples of disablots conducted in public areas as well. Snorri proposed the thought that public disablots focused on the honoring of the spirits, while private disablots focused more on healings, and private ritual workings. Historically there is proof of disir-halls, and disir shrines made out of piled stones or rocks.
An example of how some kindreds do this:
*Note: Some scholars go so far as to try and differentiate between Idises and Disir, but generally they are viewed as the same thing.
Fylgjur, not to be confused with fylgja, are female protective/guardian spirits who often were attached to a specific individual when they were born. It's said that a person can actually have more than one following them around, and that they are the carriers of that individuals specific fortune (they differ from disir in that they are attached to a single person, not a family, and thus the orlog of a family or kin relationship does not play a part here). They guard and follow a person from their birth to their death. Once the person they are attached to dies, they move on- attaching themselves to someone new, often someone in the same family. They can appear either as animals, or as females. It's slightly different from fylgja, which are the "animal totems" so to speak. I like to separate the two by adding either "female" or "animal" in front of the word fylgja. Appearance wise, they are described in a variety of ways: When being helped my one of them, they are described as very beautiful women, very appealing and lovely. When serving as an omen, they are described as looking dead, and grim. And when preparing for a battle or war, they are seen as ogresses- giant women.
They are often seen in dreams and visions, and can be seen by some through trancework and traveling. As the fyljur represents the persons luck, fate, fortune- it's important to pay attention if the fylgjur is attempting to saying something. While a person has the aid and help of their fylgjur- they have luck. Without said aid and help, they are in a bad situation. Just as the fylgjur look out for the person they protect, watching over them and guarding them, they can be a bad sign as well. It's thought that if you see a woman fylgja on a horse, or have a woman fylgja invite them into their home in a dream, that there is something ill-fated about to happen or that the person who sees this may even die. (Interestingly enough, throughout the lore Ran's 9 daughters often invited people into their homes before death- which is a similar concept). They were involved in battles and wars, like other wights. It was thought in the Ljosvetninga Saga that a specific individual befell misfortune due to the fact that their enemy had more powerful fylgjur.
Sometimes the fylgjur are thought to be part of the collective female spirits of the disir- though there isn't any concrete yes or no as to whether this is right or not. This would make sense though, as the Norns are thought to be Disir- and thus the fylgjur (who represent luck and some fortune) would be very similar in nature to the Goddesses overlooking fate. Another view on them is that they are "ancestral mothers". This viewpoint sees fylgjur women as being spirits that live in the land of the dead, and who personify or represent the spirit of a dead person. In some stories they are gathering the dead, leading them to the afterlife (much like the Valkyries), and the same stories describe people passing on riding the same horse their fylgjur rode- an omen of death. All of it is interesting, regardless.
*Interesting note. Ive vaguely heard of something called thusbet. This is seen as almost the complete opposite of the Fylgjur. This spirit, while accompanying a person throughout their life, is believed to be malicious in nature- always seeking to embarrass, inconvenience, bring harm to or kill an individual. Its akin to a personal demon*
"In the shade now tall forms are advancing,
And their wan hands like snowflakes in the moonlight are gleaming;
They beckon, they whisper, 'Oh! strong armed in valor,
The pale guests await thee - mead foams in Valhalla.'"
- Finn's Saga
The valkyries are, arguably, the most well known female spirits from this tradition- if only because society has had more exposure to them, and they are more commonly seen in modern stories, media, etc. Generally, they were viewed as "corpse goddesses", often shown by the representation of ravens eating rotting corpses. Valkyrie can roughly be translated to "chooser of the slain", "picker of the dead". Much like Freyja's "falcon coat", some Valkyrie were depicted as carrying "swan coats"- and thought to be powerless if caught without them (later on they became known as "swan maidens"- eventually becoming less of a "death" goddess in legend).Misconception, due to their popularity, has lead to the belief that valkyries were "fighting women". This is not true, because you will find that they were never involved in actual combat, and only rarely will you see them depicted holding a weapon.
In general, the Valkyrie are female battle spirits and the main job of the Valkyrie was to choose who would die in battle and to bring the slain to their place in the afterlife: Valhalla for some (the brave and honorable who die in battle), Folkvang for some others, and so on.It was thought that Freyja (the Norse goddess generally associated with love) personally led some valkyries down to battle, and would take some individuals to entertain them as guests in Folkvang (typically these guests were females: maidens, faithful wives to warriers, etc.) In Grimnismal it is said that Freyja takes half the slain and the other half go to Odin. Freyja is sometimes called "Valfreyja", meaning "Mistress of the Slain"- leading to the conclusion that she is the chief of the valkyries..which explains why depictions of Freyja show her from the middle up as being dressed for war, often wearing a helmet, shield, corselet and carrying a spear.
Valkyries served mead at Valhalla, trained warriors, and were also the messengers of Odin (sometimes even called his "foster-daughters"). Some were even seen to be prohpetesses, due to some sagas depicted Valkyrie phophesy the outcome of an oncoming battle. In this way, they "weave' the future of individuals- much like the Norns. It was believed Valkyries had war-fetter, or battle-fetter, which allowed them to bind warriors in panic and terror, while releasing others from this state- altering the course of battle. Due to this, they were commonly honored as disir and given sacrifices as Disablot. Valkyries even went beyond the battle field. They were said to impart great wisdom in humans when some were encountered (an example of this can be found in Sigrdrifumal): they shared knowledge on galdr, the runes, battle and strength, codes of conduct, etc. Beyond even this: Some were said to protect specific warriors who had won their favor, either by warning them through dreams or directly altering that persons fate in this manner. "It seems that in certain cases, the valkyrie might become identical with the fylgja entity (see the article on Asatru). In such a role, the valkyrie guides and protects her chosen human, and may become his lover. She teaches him the ways of Odin, and brings him wisdom and inspiration from the god, and when the time comes she kills him and brings him home. This kind of relationship can be seen in the Volsunga Saga, between Sigurd and Brunhilde/Sigrdrifa, and in the Lay of Helgi, and hinted at in the story of Wayland."-Uppsala
Norse Mythology: A Guide to Gods, Heroes, Rituals, and Beliefs By John Lindow
Teutonic Mythology, Volume 1 By Jacob Grimm
The Celtic And Scandinavian Religions By J. A. MacCulloch