The unknown is a very scary element. For example, in a short horror story, when you hear strange noises but don't know what's making them. It creates a sense of fear and anticipation.
For me, 'The Outsider' by H.P. Lovecraft is extremely scary. The concept of a being that is so alien and terrifying is just bone - chilling. 'The Open Window' by Saki also gives me the creeps. It has a great twist at the end that makes you shiver. Another really scary one is 'The Black Cat' by Edgar Allan Poe. The way the narrator's relationship with the cat deteriorates is truly horrifying.
A very frightening Quora short horror story involves a nurse working the night shift in a hospital. She was walking down an empty corridor when she heard the sound of a wheelchair moving on its own. She followed the sound and it led her to an old, locked room. Through the small window in the door, she saw a patient sitting in the wheelchair, but the patient had died days ago. The idea of a dead patient's spirit still lingering in the hospital is what makes this story so terrifying.
The unknown. In short horror stories, often what you don't see or understand is the scariest. For example, in 'The Red Room', not knowing what is making the noises in the walls creates a sense of dread. Another element is the isolation. When the characters are alone, like in 'The Yellow Wallpaper', it amplifies the fear.
Ghosts and spirits play a big role in scaring people in these stories. They often come with an eerie presence. Like in a story where a spirit haunts a particular place. It might be an old house or a lonely road. The spirit's actions, like making things move or whispering in a cold voice, are really terrifying. Also, the cultural beliefs and superstitions in Tagalog culture add to the scariness. Things like the idea of vengeful spirits due to wrongdoings in the past are quite spooky. It makes the horror more relatable to those who grew up with these cultural beliefs.
Sudden twists. Like when you think a character is safe and then suddenly they're in mortal danger. In a short story, this can be really shocking. For instance, a person thinking they escaped a haunted place but then finding out they're still trapped in some other way. It plays on our sense of false security.
A story about a doll that moves on its own at night. The owner would wake up to find the doll in different positions every morning. One night, she heard the doll giggling and saw its eyes following her around the room. It was terrifying.
The appearance of the clown is often a very scary element. Their exaggerated makeup, big smiles, and colorful yet often tattered costumes can be quite unnerving. For example, in 'It', Pennywise's white face with red lips and yellow eyes is terrifying.
The ghosts are often really scary. Like the white lady, her pale appearance and sudden appearance in the middle of the night can send shivers down your spine. Also, the idea of being haunted by the spirits of the dead in places like old houses or lonely roads is very frightening.