It could be the context in which the rats are used. If they are associated with a dark, spooky place like an old attic or a haunted cellar, it adds to the scariness. Also, if the rats seem to have some sort of malevolent intelligence or are controlled by an evil force, that makes it even scarier.
In the 'rat story' from 'Scary Stories to Tell in the Dark', the use of rats is a classic horror trope. Rats can be extremely menacing. They might be depicted as having an almost supernatural ability to move quickly and swarm over things. Their presence can symbolize decay and the breakdown of a safe environment. For example, if the story is set in an old, dilapidated house, the rats add to the overall sense of dread and the feeling that something truly evil lurks there.
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 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.
Well, it's scary because it takes something ordinary like a pimple and twists it into something truly horrifying. Our bodies are supposed to be familiar to us, but when a simple blemish becomes a source of evil or the unknown, it shakes our sense of safety. Also, the idea of something growing or changing on our skin in a way that we can't control is deeply unsettling.
One factor is the setting. If it's in a dark and isolated place, it immediately sets a spooky mood. For example, if Ramon is in a forest at night, the darkness and the sounds of the forest can be quite menacing.
The unknown factor could make it scary. If the raspberries are presented in a way that their origin or nature is a mystery, it can be really frightening. For example, if they seem to appear out of nowhere in a desolate place.
The unknown nature of the cat makes it scary. We don't know what it's really up to.