The architecture of the house itself can be a source of fear. Some houses in scary novels have strange layouts, like endless corridors or rooms that seem to change shape. In 'House of Leaves', the house has a constantly shifting and unknowable layout which confuses and terrifies the characters exploring it. The darkness and the creaking sounds that old houses often make also contribute to the overall sense of dread.
The isolation of the house makes it terrifying. If it's in a remote place, it gives a feeling of being cut off from the world, with no help nearby.
The old and gloomy house itself makes it scary. It has a long history full of mystery, and the idea of a house with seven gables gives an impression of something strange and foreboding.
The unknown elements make a scary story terrifying. When there are things that the characters and the readers don't understand, like a strange noise in the dark or a figure that appears and disappears without explanation, it creates fear. For example, in a haunted house story, if there are unexplained cold spots or voices, it gives a sense of unease.
The number 666 is often associated with the devil in many cultures. So, when it's part of a story, it immediately gives a sense of the presence of evil. For example, if a story involves a place marked with 666, our minds automatically think of it as a cursed or haunted location.
The psychological aspect of it. The characters' descent into madness as they try to figure out the mysteries of the house is quite disturbing. It makes you question your own perception of reality, which is a very frightening idea.
The unknown element makes them scary. In really terrifying stories, often there are things that are not fully explained. For example, in a story about a haunted doll, we don't really know how it can move on its own or why it seems to have a malevolent presence. It's this mystery that sends chills down our spines.
The appearance of clowns can be very off - putting. Their exaggerated features like big mouths, large eyes, and colorful yet often strange makeup can seem menacing. Also, they are often associated with the circus, which has an element of mystery.
Maybe it's the use of vivid and gory details. For example, if it describes some grotesque monsters with sharp teeth and blood - red eyes. That kind of visual image can easily send shivers down one's spine.
The fear of death. In murder scary stories, the act of taking someone's life is central. It makes us realize how fragile our own lives are.
The anonymity. Since 'Momo' is often an unknown entity, it creates a sense of mystery and fear. You don't know who or what it is that's threatening you.