One example could be 'She heard a noise downstairs. When she went to check, the last thing she saw was a shadowy figure grinning.' Another might be 'He thought the old house was empty. As he turned around, a pair of red eyes stared back from the darkness, and then he was gone.'
Well, in these types of two - sentence horror stories, a common one could be 'The little girl opened the closet door. Out jumped a creature that dragged her into the abyss of the closet, never to be seen again.' It shows how quickly evil can triumph in just two sentences. There could also be 'The hiker took a wrong turn. In the thicket, a faceless entity emerged and chased him until he could run no more.' These stories play on our fears and the suddenness of evil's victory.
It creates horror by being concise. In just two sentences, it sets up a normal situation like 'She walked into the abandoned asylum.' and then quickly turns it into something terrifying like 'The doors slammed shut, and a howling filled the air.'
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.
Story 1: I woke up to a cold hand on my face. When I turned on the light, no one was there.