Dark settings create mystery in a story in multiple ways. Firstly, it distorts perception. The characters and readers can't be sure of what they're seeing. Consider a dark, abandoned mansion. The creaking floors and the shadows on the walls could be anything. Secondly, it heightens the senses. Sounds seem louder, and small movements are more noticeable. This makes the reader feel as if they are in the same uncertain situation as the characters, thus creating a strong sense of mystery.
Well, when there are dark settings in a story, it's like a veil is drawn over the normal world. The lack of light hides things. Say, in a dark alley in a story. We don't know who or what is there until something reveals itself. This anticipation builds mystery. The characters are also more on edge in such settings, which adds to the overall sense of mystery.
In The Dark Tower short story, King creates mystery by introducing elements that seem to defy normal logic. There are creatures and phenomena that are not of the ordinary world. The way time and space work in the story is also a mystery. It's not clear how the characters can move between different places and times so easily, and this lack of clarity adds to the overall sense of mystery in the story.
By using the portrait as an enigma. If the portrait has a strange expression or a mark that no one can explain, it creates mystery. Also, if the backstory of the portrait is only partially revealed.
A mystery short story can create tension through its characters' emotions. If the detective is frustrated or the victim is terrified, that feeling spreads to the reader. Also, withholding information from the reader until the right moment can build up a lot of tension.
They often use the vastness and unpredictability of the sea. For example, in 'The Terror' by Dan Simmons, the sea is a harsh and unforgiving environment. The characters are isolated, and there are unknown threats lurking, like the mysterious creature in the ice. This creates a lot of suspense.
One way is through the use of setting. A spooky old house or a fog - covered forest can immediately create an atmosphere of mystery and suspense. Also, withholding information from the reader. For example, not revealing the true identity of a monster or the cause of strange events right away.
The story creates horror through mystery. Since Daniel has amnesia, the player is in the dark about his past and what he's really doing in the castle. This lack of knowledge makes every discovery scarier. Also, the fact that he has made a pact with a malevolent force adds an element of doom. The idea that he's being forced to do something he might not fully understand is terrifying.
He uses ambiguous endings. For example, in some stories, the reader is left wondering what really happened. Also, his use of shadowy and unknowable settings like old, dilapidated houses or dark forests creates mystery.
It uses the element of the unknown. Since it's based on a true story, the viewers know that something really happened, but they don't know exactly what. This makes them eager to find out. For example, when the first strange thing occurs in the family's home, like a strange mark on the wall, it sets off a sense of curiosity and suspense.
The 'Call of Cthulu Dark Corners Story' creates a sense of horror in multiple ways. The very idea of the Cthulu Mythos, with its cosmic entities that are so far beyond human understanding, is terrifying. The story also uses a lot of suspense. For example, it might hint at something dreadful about to happen but not reveal it right away. The descriptions of the grotesque and inhuman forms of the creatures also contribute to the horror. And the feeling of helplessness that the characters experience when faced with these otherworldly threats makes the readers feel the same way.
Use description. For example, describe the locked room as having a strange glow seeping from under the door or making the lock look old and rusty with strange symbols on it. This immediately makes the reader wonder what's inside.