The sense of helplessness is a big factor. In many SCP stories, the characters, whether they are the Foundation personnel or the victims, are often in a situation where they have very little control. Take SCP - 999, which seems harmless at first but can cause extreme emotional distress if not handled properly. And there's no easy way to completely stop it from affecting people once it starts.
The scp original story creates horror through its abnormal and often grotesque SCP objects. For example, some SCPs are living things with disturbing appearances or behaviors.
Sixpence Horror Stories also create horror through their settings. Dark forests, abandoned asylums, and old cemeteries are common settings that immediately give off a spooky vibe. The detailed descriptions of these places, like the overgrown weeds in the cemetery or the creaking floors in the asylum, enhance the sense of horror.
The 'Midwich Horror Stories' create horror through the use of the unknown. For example, if there are strange creatures or events that the characters can't explain, it immediately makes the readers feel uneasy.
They use the unique shape of the spiral. The spiral is an unusual and often unsettling shape that can make people feel uneasy. When it's constantly presented in a horror story, it creates a sense of dread.
They often use the element of the unknown. For instance, in a story where a character hears strange whispers but can't figure out where they're coming from.
The horror could be created by a sense of the unknown. The steps might lead to places or situations that the characters, and the readers, have no idea about. It's like walking into a dark room not knowing what's inside. Also, the characters might lose control as they follow the steps, and that loss of control is a big part of what makes it scary.
The element of the unknown also plays a big role. For example, there could be hidden passages that lead to terrifying places filled with horrors that the player can't anticipate. This lack of knowledge about what's around the corner keeps the player in a constant state of fear.
They use atmosphere. Dark settings, like a fog - covered graveyard or a dimly lit cellar, are often described. This immediately makes the reader feel uneasy.
Through the use of spooky settings like old, dilapidated mansions or dark, isolated forests. These places immediately give a feeling of unease.
The stories often have unexpected twists. Just when you think you know what's going to happen, something completely different and more terrifying occurs. Like a character you thought was safe suddenly getting attacked by an unseen force. Also, they play on our fears of the unknown. Things like strange noises in the dark or shadowy figures that we can't quite make out are very common in these stories, which scares us because we don't know what they are or what they might do.