@Yaarel
If one wanted to do British faerie knights or Norse alfar as beings in D&D (in the Monster Manual) that could also be used as a PC options, how would you want them described?
Heh, this is a pertinent question. Because, as you seem to remember, some of my settings do have mythologically accurate Faerie Knights and Alfar.
It is a challenge to translate them accurately within the context of D&D rules and gaming balance.
To describe them, I start with the reallife folkbeliefs (from an academic, often archeological perspective).
Mostly, the Alfar come from Icelandic texts as well as Norwegian and Swedish contexts, such as place names, and earlier strata within later folkbeliefs.
Mostly, the Fairie come from the records of the reallife Scottish witch trials, where witches describe their encounters with various Elves. Anything that is clearly foreign, such as Christian theology can be safely ignored. Meanwhile, Shakespeare plays happen to describe the English folkbeliefs in Fairy in considerable detail when piecing together all of the comments made in passing. Works like the Merry Wives of Windsor, The Tempest, Midsummer Nights Dream, are especially useful, but also stray comments in other plays that arent really about Fairies. For example, children disguise themselves as Fairies, thereby terrifying the onlookers. We can see from this, the Fairies actually look like humansize youth, are luminous, and Humans value their fateful blessings but are terrified of their fateful curses. Moreover, the more powerful they are, the younger they appear (and likewise the more innocent but less ethically mature). So where the Fairy Queen Titania is described as a toddler, we can see she typically appears as if a human two-year-old. And so on. Generally, the English culture argued that their Nonchristian nature beings arent evil demons, just immature children. There is lots of information about Fairies when one looks for it.
The origins of the folkbeliefs are animistic nature beings. Understanding animism helps. These beings are literal features of nature.
In the Norse traditions, the Alfar are various patterns of sunlight. These military formations of sunlight comprise numerous persons. The light is a person. The light behaves the way it does because it "likes" to and "chooses" to behave that way.
In the British traditions, the Fairy are fertile soil. To see notable areas of lush vegetation, such as a cluster of trees, is itself evidence that Fairies live there. The Scottish and English traditions tend to blend Celtic folkbeliefs about Sidhe (Scot. Sith) with other folkbeliefs of Anglians and Saxons. There is some Nordic influences too. But Britain evolves its own unique folkbeliefs. There are regional distinctions. In the south, in England, the Fairies normally manifest out of the soil to appear as if small human children. But in the north, in Scotland, the Elves (aka the Sith) appear as if human adults. In all cases, the British apparitions are immaterial spirits manifesting from the soil. Some of the Scottish witches compare the Elves to a "shadow" that has a form but without any substance.
And so.
To translate these reallife ethnic heritages into D&D gaming rules is a sensitive ethical challenge. On the one hand, it is cool to preserve these traditions in interesting ways that the world today can enjoy. At the same time, caution is necessary to avoid misrepresentation or insult.
The Norse folkbeliefs translate well into D&D. Unlike other cultures that have all-powerful "gods", the different kinds of Norse nature beings are all moreorless equally powerful as each other. In the Eddas and over a hundred Sagas, there are examples of individuals, a powerful Human individual, a powerful Dvergar individual, a powerful Æsir individual, and so on, each able to defeat the other in that story. Heh, in one story, a Human punches out Óðinn and throws him overboard. For D&D, this seems identical to the concept of Character Level. The Norsesque species have features that moreorless balance with each other. A Human is just as powerful as an Æsir. But. Óðinn isnt a more powerful species − he is simply a higher level character. So the next challenge is to compare which D&D classes compare well to which Norse folkbeliefs. Generally speaking, the 5e Bard is awesome for almost every example of Norse spell effect. Of course, there are no musical instruments, the Nordic lands lacked them. The Norse mages do magic by means of thoughts (Hugar), often using speech and sometimes using novel runic inscriptions as a technique to focus thoughts. I am comfortable with translating Norse Hugar into D&D "Psionics", as the method of spellcasting. Despite the Psionic "Spellcasting Focus", the features of the Bard class work uncannily well. It turns out, basing the Bard on mythologically Celtic folkbeliefs ended up helping out Nordic folkbeliefs as well. Much of it is variations of shamanic animism. Heh, Norse mages are typically psionic Bards.
In addition to Bard, an other surprisingly useful D&D class is Paladin: the abjuration magic coheres well with Norse warrior magic. The Norse males can and did do magic, but it was a social taboo for a male to be cowardly, so it was dishonorable to use magic to harm enemies from a distance. But to use magic to heal and empower oneself and ones allies, in order to face an enemy courageously in battle, face-to-face. Hence the Paladin is awesome. Because I personally like mages, I would also use the Cleric class as a fullcaster, but flavor it exactly like the Paladin class, to represent warrior magic.
Note, the Norse nature beings are literally features of nature. The sunlight is alive, conscious, and sapient. One can communicate (telepathically) with sunlight, and viceversa. On rare occasions, the sunlight projects outofbody sotospeak to manifest in a Human form. Sometimes this form more like a ghostly apparition. But occasionally it is a full-on form of flesh-and-blood. (There is a detailed story about a mountain who becomes a human.) Note, not every sunlight mind is able to materialize in this way. If a mind does this, it is because the mind knows how to do the magic to be able to do this. Almost by definition, an Alfar who can manifest out from the sunlight must be a mage. The Alfar can also teach a Human how to do this, translating back and forth between sunlight and flesh. Viceversa, a Human can teach an Alfar some of the magic that the Human knows how to do. Even the Æsir are learning and teaching the same kinds of magic that Human mages are doing. There is no difference. Indeed, the first Human mages were taught by Jǫtnar how to magic. It is typical for Norse mages to go into a magical trance, to travel outofbody to visit with outofbody nature beings, for these beings to train them to do magic.
In D&D, the Druid class can be useful − not really for the Norse Humans − but the druidic elemental magic helps to actualize the weather magic, and similar, that the sky beings can do. Meanwhile, the Sámi mages do weather magic, and animal shapeshifting is also prominent, so the Druid with some tweaks can help toward these Nordic folkbeliefs.
From a D&D perspective, all of this is caster classes and class levels. High level casters learn how to cast higher level spells. This is true for Humans, Dvergar, Alfar, Jǫtnar, Æsir, Vanir, and Corpses. It is all levels in caster classes.
In the Scottish folkbeliefs, the Elves are immaterial spirits. The D&D 5e concept of the Fey plane works out well. The Scottish Elves are fertile soil, literally. When they project outofbody, they do so as immaterial spirits. D&D represents this well enough. The Fey Plane is an immaterial spiritworld. But the spirits moving thru the Fey Plane appear as virtual bodies whose form behaves as if a material body, or close enough to one anyway. So the Scottish Elves are moreorless like Humans when projecting out-of-soil, except they are Fey, not Material. The Elves rarely materialize into the flesh-and-blood of the Material Plane, and Humans rarely spiritualize into the immateriality of the Fey Plane, but there are stories about this kind of translation happening. For the Scottish witches and Fairie Knights, I am leaning toward the Warlock class, and Fey subclass themes, except healing magic is central. So spells like Cure Wounds and such are necessary for this kind of Warlock to have. Also notably, the Warlocks comprise a community who visit each other across the Fey-Material veil.
Anyway, in the case of Norse, Sámi, Scottish, and English folkbeliefs, it is easy to talk about Nonhuman species who are Humanoid and comparable to the Human species, and who have a strictly Human culture. For example, the Nordic nature beings speak Nordic languages and participate in local Nordic cultures and customs. Scottish nature beings speak Scots and Gaelic, and participate in Scottish cultures and customs. These are Human cultures.
