1-Lumberjacks, cattle drivers, and hunters who most people normally put at odds with forest fairies in modern day books really had a symbiotic relationship with them. For example, in Germany a forest god would chase down and kill forest fairies like rabbits, but the lumberjacks would draw magical symbols on trees which could keep the fairies safe.
In Russia herdsmen would provide food for the fairies who would protect their herds. And hunters obviously prayed and made offerings to the forest fairies who provided them with game.
Indeed all three of these people's had such a close relationship with the fairies that they were often considered magical, essentially witches in their own right.
2-Many of the spirits of the forest are the spirits of the human dead. Tree spirits, rock spirits, mountain spirits are often the spirits of the dead. Indeed the forests and mountains were often believed to be the afterlife, acting as both heaven and hell.
3- Vampires and forest lords are often confused with each other in lore, because they are so much alike its often difficult to distinguish one from the other. Forest fairies, after all are among the scariest of all fairies. And indeed the devil in fairy tales who wishes to buy people's souls is often originally a forest fairy, who wants to buy people's souls.
4-After all forest fairies want human workers. They would often hire and or enslave humans to watch their animals, to serve their feasts, to watch their children, and more. For those of you looking for writing prompts there are a number of tales about people who become shepherds for fairies, watching their cattle. Or stories about people who become babysitters for the fairies children. You could even add a little action by having this happen during a time when the fairies were at war with each other.
5-As time went on it was a natural transition for forest fairies to move into people's houses, becoming essentially household fairies. Indeed people would make sacrifices to forest fairies in order to get their aid within the household as the forest fairies approval was important to a households success.
6-In fact whole cities were founded because of forest fairies who agreed to become the patron of the city's future. Sometimes these fairies even married the city's founder. Thus the children of a city could be the children of a forest fairy. In Greek lore Arcadia was founded by a hero who saves a tree nymph. In return she agrees to sleep with him and the two of them have many children, whose children become the first Arcadians.
7-Despite their domesticating nature, forests also represented freedom and an escape from society. In Japan many women would escape abusive husbands and hard society by escaping with a forest fairy. In Selkup lore (hunter-gatherers in Siberia) a spirit caled the Muli qup, which looked a lot like a satyr, would teach women how to hunt on their own so they could leave their abusive husbands.
8-As part of this forests came to be associated with shamans and witches because this is where they would often learn their craft. Specifically they were often possessed by spirits who caused them to go running into the woods, or kidnapped by them. Often they would emerge a few years later, feral and covered in moss. After this they could use their friendship with the spirits of the forest to perform magic.
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