What do faeries do with kidnapped human children?

Question

Fairies -- sidhe, elves (not the Tolkien type), fairy folk etc -- have the bad habit of replacing human babies with their own for whatever reason, creating changelings ("children that have been changed, replaced"). A changeling grows among humans and later discovers his true calling.

But what happens with the kidnapped human children? Is there some sort of consensus as to what fairies actually do with them? I'm assuming it's nothing good, but besides a brief note in the Wikipedia saying that "in Scottish folklore, the children might be replacements for fairy children in the tithe to Hell" there is very little information about the possible fate of such kids.

EDIT: While I'm interested in all possible cultures, I'm especially interested in Ireland and Britain.

Answer 1

"Is there some sort of consensus as to what fairies actually do with them?"

No. Because there is no consistent Hiberno-British folk mythology. Any apparent or alleged consistent anything about that was made up (or, let's be generous, synthesised) later.

You can look at any attempt to record folk traditions from various places and periods, and they will be different. Some suggest both good and evil purposes in the kidnappings. Sometimes they are raised and live among the fairies in joy, in some they are used as servants (treated cruelly or kindly), and some they are used for torturous entertainment (though possibly only once they've grown up a bit).

The nature of changelings varies in different sources as well. In some they are fairies pretending to be human children - in at least one reference I read, that's the whole purpose of the deception, rather than the taking of the child - they want human milk. In those, the fairy will sneak off at some later date. In others they are fairies who don't know they are fairies pretending to be human children, and they awake to their otherly nature later. In yet others, they are short-lived magical constructs and sicken and die.

The versions recorded by folklorists from prior centuries are of no inherently greater value than those 'created' by fiction writers in the second half of the twentieth century, or in the early years of the twenty-first. We have so little to go on in terms of reliable sources that it's all anyone's guess.

Answer 2

I've heard, that they take children, could find several fates, they could be made slaves/servants, they could be raised as one of the fairies, living long happy lives, sometimes returning to the human world, as powerful witches, sometimes the child was simply killed, or even eaten. The one taken could be an adult, that the fair folk found interesting or useful, they could also be made slaves, midwives, or even lovers. It is said that children born from fairies and humans would be very skilled for sorcery (especially females) more powerful than any human witch and could become more powerful than the fairies themselves, for they would have the magic of a fairy, and the human connection to magic, that allows us to perform witchcraft. An example of this would be Morgana Le'Fay, arguably the most powerful witch of all time

Answer 3

Those humans are possibly raised to serve fairy folk. Human females are said to be more efficient for reproduction purposes. Males are kept to serve the fairy folk.

Answer 4

Faeries swapped their offspring with human babies because faerie children were weak and frail, and that's why they got the human mothers to raise their faerie children; so that they could grow strong. I'm not too sure, but I think it's commonly thought that the humans they steal are slaves and when the faerie child is older and stronger, they take it back, and keep the human children as servants. But it's widely speculated and there isn't a concrete theory.