They often involve being trapped, like in the riddle of the room with no exit. Trapped situations are inherently scary. It makes you feel the helplessness of the character in the riddle.
One '15 second horror story' could be: You wake up in the middle of the night. The room is pitch - black. Then you hear slow, heavy breathing right next to your ear, but you're alone.
One horror story could be about a haunted mirror. In the '7 second riddles horror story', there might be a mirror that shows a different, terrifying face every time someone looks into it for 7 seconds. It drives people mad as they keep seeing these grotesque images and can't escape the mirror's curse.
One story could be about a haunted mirror. A girl noticed in the mirror that there was always a figure behind her, but when she turned around, there was nothing. Every time she looked back at the mirror, the figure got closer and closer until one day she saw its face, a distorted and terrifying visage. And then she vanished, leaving only the mirror with a dark shadow inside it.
One second date horror story could be when the person you're with suddenly starts talking non - stop about their ex - lover throughout the whole date. It's really off - putting as you're trying to get to know each other, not hear about their past relationship drama.
One example could be 'In the old attic, I found a doll. Its eyes followed me. Then it smiled.' Another might be 'Walking alone at night, a hand grabbed my ankle from the sewer grate.'
One example could be 'I woke up in the middle of the night. There was a figure at the foot of my bed. When I blinked, it disappeared.' Another is 'Walking in the old attic, I heard a child's giggle. I was alone.'
They are effective because they quickly set a spooky mood. There's no time for long build - ups. For example, just saying 'I opened the closet and a hand grabbed me' gets right to the horror.