I went with my niece to see the latest film. It was okay. It's missing something that the earlier films had, some newness, perhaps. It's like the wizard world is too familiar now, or something.
Anyway, in the middle books, Rowling introduced elves; mostly in that film, they're house elves, basically slaves. Disgustingly, in the book, the house elves of "good" masters (as at Hogwarts) like being house elves. It's only when they have Malfoy type masters that they really hate their slavery.
But that aside, the elves seem very powerful in these texts. Really, really powerful. They're innately magical in ways that humans aren't, it seems.
So I have two questions: how did they get enslaved? And how come they don't take over?