I Never Saw Her Again
When I was about 10, my sister brought over two of her friends, who were around 16 at the time. We were bored, so I convinced them all to play hide and seek.
I lived in a big house that had several access points to a large attic. The house was also very “spooky” and was visited by priests once while I lived there as a child. The three girls dispersed and went to hide while I counted down from 50.
While counting down, I was interrupted by the most haunting screams I have ever heard in my life. I was petrified. One of the girls sprinted down to the kitchen, screaming and in tears. After calming her down, we asked her what had happened. She said that as she was hiding in the attic, she had seen a demon sitting at the other end of the attic, looking at her.
I never saw her again after that.
Story credit: Reddit / Igloomasterp