You know, this imprisoning of people is very much in keeping with _authentic_ elf-legends. That is, many traditional tales of elves, fairies, leprechauns, etc. involve them keeping humans as prisoners. If you ever see the old, old Disney movie "Darby O'Gill and the Little People" (featuring Sean Connery before he even did his first James Bond film!), you'll see that the imprisonment theme is part of it.
Joseph Ravitts, author of "Southward the Tigers"