A cliché of faery lore is that the fairies grant our wishes, often in threes because this is a magical and significant number (at least in Christian tradition). This is more the substance of fairy-tales and fairy godmother stories than authentic British folklore, but it’s not entirely without foundation in native accounts.
Mermaids seem especially prone to granting triple wishes. Furthermore, as the Cornish story of Lutey and the mermaid demonstrates, mermaid vengeance may be postponed (as I recently described for the faeries too). The mermaid first granted Lutey three wishes as a reward for returning her to the sea when she’d become stranded, but then refused to let go of him when they were in the surf, instead trying to drag him under the water. The barking of his dog and the sight of his cottage on the shore broke her spell, and with a flash of his knife he forced her to let him go. Nevertheless, the mermaid promised to return after nine (three times three) years- which she did, seizing him from a fishing boat out at sea. The mermaid in the related Cornish story, The Old Man of Cury, grants a single wish, as does the Manx mermaid who falls for a man who woos her with gifts of apples.
The fairy women of Scotland seem especially inclined to grant wishes to humans. These skills may be taught, or exchanged for sex, or they may be given as rewards. Often, the grant is offered conditionally: the recipient can have either ‘ingenuity without advantage’ or ‘advantage without ingenuity.’ One will be clever and highly skilled, but will never be rich; the other will make the man prosperous, but he will be stupid. Abilities in crafts or music are often bestowed; even a great skill in thieving can be granted, apparently. Sometimes, too, these awards are not really gifts at all, and a price may be exacted, which can even be the eventual forfeit of the human him or herself. We saw this with Lutey; in the Scottish tale of Peter Waters of Caithness, he met a fairy woman at a well and she spontaneously offered to endow him with great prowess, either as a preacher or as a piper. He chose to be a piper and she even gave him a set of pipes. All she asked was that, in return, they meet again after seven years. In the meantime, he won great fame and fortune for his music but when he duly returned to meet her at the well, he was never seen again (J. G. Campbell, Superstitions).
An unusual Scottish Gaelic story builds upon this general idea. The fairy queen (who is generally identified with Fann, the embodiment of skill) was grieved by the lack of wisdom amongst many women in the world. She therefore breathed on the fairy flax plant and issued a summons to every woman in the world to come to her knoll to be endowed with wisdom. Many came and the queen appeared before them, carrying a limpet in which there was the ais or skill of wisdom. Each woman was invited to drink from the shell, according to her faith and desire. Sadly, the cup ran dry before all could drink (Carmichael, Carmina Gadelica, vol.2).
There are other ways to get what you want from fairies though. At Bewcastle, in Cumbria, there is a stone to which you can whisper your secret wishes; the fairies will then help you. In several other instances, wishes are granted and skills bestowed as the result of bargains- although these deals are not always willing entered into by the faeries. A boy who stripped turf from a faery knoll was persuaded to replace it on the basis that he would be helped in making the best chanter possible for his bagpipes. A girl who agreed not to tether her cows on a knoll was then directed to grazing that never ceased and produced very rich milk. Equally, a man who stuck his knife in the doorway of a faery hill refused to remove it until he had been granted piping skills.
All in all, there is a curious transactional relationship between humans and supernaturals. The faeries constantly and unrepentantly steal from us and use our property and possessions, but they will spontaneously grant valuable knowledge and skills or make gifts of gold. They will reward good deeds but at the same time lavish wealth on favourites who may seem to be chosen at random. In some cases love motivates their actions; in other cases they find themselves forced begrudgingly to comply. It’s a complex exchange of generosity and obligation, part of the tangled and frequently tortuous relationship that we have forged with the over the last thousand years or more of cohabitation on these islands.