Use simple but spooky words. For example, 'Footsteps, but no one'. The words 'footsteps' immediately create a sense of someone or something being there. But when you add 'but no one', it becomes a horror story in just five words. It makes the reader wonder what is making those footsteps if there's no one there.
Combine two scary ideas. Say 'Coffin, open, empty inside'. The idea of a coffin is already spooky. When you say it's open and empty inside, it gives a feeling of something unnatural. Maybe something was supposed to be in there, or something has escaped from it.
Think of a simple, creepy situation like 'Lights out. Something moves. Shadows.'
Just think of a sudden, dark twist. For example, 'He walked. The shadow had no feet.'
Just focus on fear. For example, think about things that scare you like a haunted house, and then sum it up in five words like 'Haunted house, no escape.'
Evoke strong images. Consider 'Bloody handprint.' This three - word phrase immediately brings to mind a violent or spooky scene. It's a visual that is both simple and very effective in creating horror.
Use strong imagery. For example, 'Blood on white sheet'. Pick words that evoke fear like 'dark', 'death', 'lost'.
Think of fears. 'Darkness fell, something grabbed my leg.' Darkness is a common fear, and the sudden action of something grabbing your leg is very scary in just 10 words.
In the abandoned house, I found a diary. The last entry said 'They're here'. Then I heard scratching at the door.
Use simple, spooky elements. For example, 'Dark room. Strange noise. Gone.' Just pick a common, yet eerie setting like a dark room, add an unexplained and menacing sound, and then a final word that implies something bad has happened.