Maybe it's the unknown aspect of Harold's situation. If we don't know much about what's going on with him, it creates a sense of mystery and fear.
The unknown aspect makes the dark Harold scary stories so scary. We don't really know who or what Harold fully is. Is he a ghost, a demon, or something else? This mystery creates fear.
His actions might make him scary. For instance, if he stalks people in the story or does something really cruel to his victims. Also, the mystery surrounding him. If no one knows where he came from or what his motives are, that adds to the scariness.
The things that make 'harold the scary story' scary could be multiple. If Harold is a menacing character, his actions like stalking or making strange noises in the dark would be scary. Also, the setting of the story might be spooky, like an old abandoned place. And the unknown elements about Harold, such as his motives or where he came from, can add to the scariness.
His appearance might make him scary. A scarecrow is already an object that can look spooky, and Harold is likely to be dilapidated with torn clothes and a menacing stance.
His appearance. His ragged clothes, his stitched - up face, and his straw - filled body give him an eerie look. It's not something you'd expect to see moving around, so when it does in the stories, it's really scary.
In the world of scary stories, Harold's costume is scary because it defies explanation. It has the power to change the wearer's behavior, like making them do things they wouldn't normally do. It also seems to have a connection to a realm of the supernatural. For instance, it might be associated with ghosts or other malevolent spirits. The fact that it can cause such abnormal and frightening experiences makes it extremely scary.
The unexpected twists. Just when you think you know what's going to happen, something completely different and terrifying occurs. For example, a seemingly friendly character could turn out to be something evil. Also, the use of common fears like the dark or being alone in a strange place really amps up the scariness.
The fear of the unknown in dreams. We don't really have full control in our dreams, and in this story, that lack of control can be terrifying. For example, not being able to run away from a threat in a dream.
The fear of the unknown in dreams makes it scary. We don't fully understand our dreams, and in this story, that lack of understanding is exploited.
In the Scarecrow Story in Scary Stories to Tell in the Dark, there are multiple elements that make it scary. The fact that scarecrows are human - like in shape but not human at all is a big factor. It makes us uneasy because it's a distortion of the human form. Also, the way the story builds up the mystery around the scarecrow, not revealing its true nature right away. We start to wonder what it is capable of, and our minds start to imagine all sorts of terrifying things, which is what makes it so effective at scaring us.