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.
Well, it could be that the 'cast' is about the range of emotions that these one - sentence horror stories evoke. The 'cast' may include feelings such as sudden dread, unease, and a sense of the uncanny. When we read these stories, the 'cast' of emotions is quickly and powerfully summoned, making them effective despite their brevity.
There was a story that only had one sentence, but it was very scary after listening to it:
On that dark night, a lonely man stood on the top floor of an abandoned building. He kept listening to the heavy footsteps coming from downstairs, but he never saw anyone. Until he saw the door that he had always thought was safe. The paint on the door had faded, revealing a mottled wooden surface. He pushed the door open and found that the room was empty, but there was a strange aura that made him feel uneasy. He kept walking until he saw a dark corner where there was a imprisoned soul, and his soul was being sucked away.