Of course. 'The door opened on its own. A shadow slid inside.'
Sure. Line 1: I found a strange key in the basement. Line 2: When I used it on the locked door, a blood - curdling scream came from inside.
The mirror showed my reflection smiling. I wasn't smiling. I ran.
I walked into the forest. The trees whispered my darkest secrets.
One line: 'The artist painted his dream on the canvas, then vanished into it.'
Use the element of the unknown. For example, 'There's a noise in the attic, but no one's been up there for years.' By leaving the source of the noise a mystery, it creates fear. People's minds will start imagining all kinds of terrifying things.
Once upon a time, a cat chased a mouse. The mouse hid in a hole. Simple yet full of action.
I heard a knock at the door. I opened it, no one was there, but I felt a cold hand on my shoulder.
They are effective because they are concise. They quickly get to the point of horror without a lot of build - up.
I was alone in the attic. Then I felt someone whisper my name in a voice I didn't recognize.
Another one might be 'The old doll in the attic blinked. I'm sure it did.' This simple line creates a sense of unease as dolls are often associated with the uncanny. The idea of an inanimate object like a doll showing signs of life is quite terrifying.