Are you looking for something for a horror story, or does it not really matter? Since we're on the topic of Eastern folklore there's the oni baba, a Japanese mythical humanoid creature. She takes the form of a very wrinkly and elderly woman with long grey hair, but she's actually much more dangerous than that might initially sound. The oni baba lives in an isolated little hut in a mountain somewhere, letting lost and tired travellers stay the night at her little abode. These travellers will often hear a strange sound in the night, and if they open their (traditional Japanese wooden sliding) doors slightly they'll see the old woman sharpening a large kitchen knife against a stone, laughing manically with a twisted look of malevolence on her face. Sometimes they'll live to tell the tale, whilst others end up getting gored and eaten by her in the night.
I've also seen some variations of this in popular Japanese culture. In the manga Detective Conan there was a scenario similar to the above where (I think, but don't quote me) a group of people were stuck somewhere remote on a mountain, but luckily they managed to stay at the house of an elderly lady. One of the people staying was murdered in the night and, you guessed it, somebody spotted the old lady sharpening a knife, leading her to become a suspect. It was in a more modern setting and had a less supernatural feel than the traditional oni baba story, but the idea was the same.
There was this children's picture book called Yamanbasan where the protagonist was based on the oni baba myth but just much more amicable. She was still a shrivelled up old lady but she didn't go around stabbing people with a knife or luring people into a trap. I don't remember the plot details but she seemed to enjoy running up and down mountains at incredible speeds and had superhuman jumping abilities despite her age.
