A good horror sentence is 'In the dark attic, a pair of unseen eyes watched every move she made, following her like a predator.' This creates a sense of being observed in a spooky, isolated place. Another example is 'The cold wind whispered through the graveyard, carrying with it the faint sound of a long - forgotten lament.' It sets a very eerie atmosphere with the combination of the cold wind, the graveyard, and the faint, mysterious sound.
Well, how about 'The clock on the wall stopped ticking, and then a cold hand gripped her shoulder from behind.' This combines the sudden malfunction of a common object like a clock with the physical touch of something unknown and cold. Or 'The moon was blood - red, casting an ominous glow over the desolate town, where death seemed to lurk around every corner.' The description of the moon's color and the desolate town creates a very menacing and horror - filled setting.
Here is one: I woke up in the middle of the night. When I turned on the light, I saw a figure at the foot of my bed. Another one: I heard a baby crying from the attic. I climbed up only to find a doll with a blood - stained dress.
Suddenly, a hand reached out from the darkness. I closed my eyes, waiting for the worst. But when I opened them again, I was in my own bed, safe and sound. It was as if the horror had been a cruel joke played by my overactive imagination.
Strange sights. Like seeing a distorted face or an unknown shadow can be very effective in a '1 second horror story'. The unexpectedness of seeing something that doesn't belong makes the horror immediate.
She thought she had escaped the haunted house. But as she stepped onto the porch of her own home, she felt the same icy grip on her ankle. The horror had followed her home.
One could be 'The shadows in the corner seemed to writhe and twist, as if alive.' Another is 'A cold, clammy hand brushed against her neck, sending shivers down her spine.' And 'The silence was broken only by the slow, methodical drip of something unknown in the darkness.'
You can use 'The old, creaking floorboards groaned under his feet, as if warning him to turn back, but he pressed on, oblivious to the doom that awaited him.' This sentence is effective in a horror story. The description of the floorboards as old and creaking gives a spooky setting. The idea that they seem to be 'warning' the character adds an element of the supernatural. And the fact that the character ignores this warning and is headed towards doom ramps up the tension for the reader.