The malicious spirit Kuchisake-onna of Japanese folklore wears a mask and carries a sharp object. When you meet her, she asks whether you think she is beautiful. If you answer no, she kills you. If you answer yes, she removes her mask to reveal that the corners of her mouth have been slit open to her ears.
Then she repeats her question. If again you answer no, she kills you. If you answer yes, she cuts your mouth to resemble her own.
Happily, there are at least two ways to escape: describe her appearance as average, or throw hard candies to distract her.