They can be. Some people really enjoy the quick thrill and suspense that two-sentence horror stories offer.
Another really scary one could be 'My phone rang at 3 am. The caller ID said it was me.' It plays on the idea of the self being something other or unknown, and calls at that time are always spooky.
Story 1: I woke up to a cold hand on my face. When I turned on the light, no one was there.
Some might be based on real experiences or fears, but many are fictional creations for entertainment.
One way to sentence horror stories is to build suspense gradually. Start with an ordinary setting or character and then introduce strange elements little by little. For example, you could begin by describing a normal day in a small town. Then mention a strange noise that no one can identify or a person who behaves oddly. Use vivid language to describe the uneasiness that starts to spread among the characters. This makes the readers feel on edge as they wonder what will happen next.
I think 'The clock stopped at midnight. Then I heard footsteps.' is quite scary. It gives this feeling of something ominous starting right at a spooky time.
I'll share this. I found a diary in an old attic. The last entry said 'They're coming for me tonight' and then the handwriting turned into scribbles. I started to hear scratching noises on the attic door right after reading it.
They are concise. For example, 'The phone rang in the dead of night. It was my voice on the other end asking for help.' In just two sentences, it creates a sense of dread. They often rely on the unexpected. Like 'I found a door in my basement that wasn't there before. When I opened it, a cold hand grabbed mine.' It takes a normal situation and twists it into something terrifying.
Well, the one where 'I woke up in a coffin. As I screamed, I realized I was buried six feet under.' is quite terrifying. Just the thought of being trapped alive underground is a nightmare.
Here's one: 'The last page of the book I was reading had my name written in blood.' Reading is usually a safe and solitary activity. But when something as sinister as your name written in blood appears on the page of a book you're reading, it creates a sense of dread. It's as if the book is somehow connected to you in a very dangerous and unknown way. It could mean that there is a malevolent force that has targeted you specifically through the book.
One could be 'I woke up to find my reflection smiling back at me, but I wasn't.' It creates an immediate sense of unease as it plays on the idea of something being wrong with one's own reflection, which is often associated with the self. It makes you wonder what has taken over your appearance.