appearantly no-one has mention näkki and vodyanoy
I still am bit scared of mörkö / mrs. groke but at the same she's my favorite character of moomins since I read a book and realized that groke's been misunderstood!! if someone wants me to explain myself how groke's misunderstood then sure, just tap me on shoulder ^^
I'd say elves--not modern elves like the ones from Lord of the Rings or World of Warcraft, but the more traditional elves that were beautiful in the front, but had gaping, rotting holes in their backs that if you saw the holes, you'd find the elf is actually hideous, and would kidnap people and use them as...children don't need to hear about this kinda thingslaves.
That said, everything everyone else mentioned is pretty scary.
In our country the Philippines, there is a creature called manananggal.
She is a woman that can seperate her body in half through the waistline and flies at night with her upper body (and leaves the other half in a hidden place), looking for pregnant women to feed on or sometimes children. It is said that the only way to kill a manananggal is to put salt on her lower body, so that she can't re-connect with it anymore. When the sun comes up and when the creature still can't return to her body, she gets burned by the sunlight.
Even today, there are some people who have encountered a manananggal, however, none of them have sufficient evidence.
I was gonna choose this too. wink I've read a lot of myths but nothing's scarier than the manananggal and its cousins (other variations) throughout Southeast Asia. We have one such item in The Nightmare (E.I.). The pose is called Penanggalan.