The Elle Folk - random myth

Danish creatures that, I guess, appear much like humans excepting the males are very old looking and the females have hollow backs (whatever that means). They live in the Ellenmound (Elemounds) or the Ellemoors. The women sing or play the lyre so beautifully they can entice hunters and travelers in their direction. Then they kill them. Then can breathe out a vapor which can kill men. They are malevolent beasts and best avoided. They enjoy dancing beneath linden and lime trees, have custom and a king  in the nature of man and an army which turns to a forest in the day.

Crazy creatures.Good idea fodder.