Here's another: 'The old doll stared at me. Then it blinked.' This is a simple yet creepy example from such horror stories. The first sentence sets a somewhat normal but eerie scene with an old doll just staring. The second sentence, where it blinks, takes it to a whole new level of horror as dolls are not supposed to blink. It plays on our expectations of inanimate objects and violates that in a very spooky way.
One could be 'I woke up to a cold hand on my shoulder. It was my own, severed in my sleep.'
One example could be 'I woke up to find a cold hand on my shoulder. I live alone.' Another is 'The old doll in the attic blinked. It was facing the wall before.'
I woke up to a strange noise. When I looked under the bed, I saw a pair of eyes staring back at me.
Here's another: 'I saw my reflection smile at me. I wasn't smiling.'
One example could be: 'I woke up in the middle of the night. There was a figure standing at the foot of my bed with no face.'
One example could be: 'I woke up to a cold hand on my shoulder. In the mirror, I saw no one behind me.'
Another is 'The old house was silent. Then I heard the sound of a rocking chair moving on its own.' Here, the first sentence sets a spooky scene of an old, quiet house. The second sentence adds the horror element by introducing an unexplained and creepy sound of a rocking chair moving without anyone seemingly around to move it.
The clock stopped ticking. Then I heard the echo of a heartbeat that wasn't mine.
They rely on the element of surprise. Like 'The mirror showed my reflection. But it wasn't me.' In just two sentences, they can subvert our normal expectations. We expect to see our normal self in the mirror, and when that's not the case, it creates an immediate sense of horror. The quick setup and twist is what makes them so effective at scaring readers.
Story 1: I woke up to a cold hand on my face. When I turned on the light, no one was there.
One example could be 'I heard a scratching at my window. When I opened the curtain, there was a faceless figure.' Another is 'The old house was silent. Then I saw a pair of glowing eyes in the dark corner.'