Or: What I have learned about scary stories in the three years of Schattenspiele.
First off a rhethorical question: What do an erotic story and a scary story have in common? Answer: What you don´t see is what´s the most interesting. In other words: Tension and build-up, with the goal being the best possible stimulation. While shocking moments are important, they should be used sparingly, even if that does not seem logical at first. But I´ll elaborate.
There are different kinds of fear, let´s just put them into three categories for now:
Unsettling: Something is off, something is alarming or even just uncomfortable. You might not be able to put your finger on it, but it´s there (probably) and it´s haunting. It might or might not be enough to get your imagination starting.
Scary: You know that something is there and it´s out to get you. It´s not here yet, though, but you know that it´s going to come, inevitably and with no or only a small hope of avoiding it. And when it happens, it´s gonna be BAD.
Shocking: It is there, immediate, no distance in between and the self loses itself for a moment in a pure, overwhelming moment of fear. Maybe it came out of the blue, maybe there was a build-up, but the result was even worse or something entirely different, but equally terrifying as what was expected.
Now what an author might want at the end of the tale is “shocking”, but what they really aspire most of the time is “unsettling” or “scary”. Why? Because while shock is indeed the most intense feeling, it´s over soon. I bet every one of us has witnessed a jump scare in our lives. Yes, it´s bad, but when it´s over, it´s over and a sweet release of endorphin ensures us that we are indeed still alive. Shock alone only releases tension, is what I want to say. You need context to make it last. You want to make it last. And yes, horror authors have to be sadists. Actually, most authors have to be sadists. Comes with the territory.
What you need to prepare a good scare is a “dark hallway”. A “dark hallway” is something we all encounter in our daily lives that unsettles us irrationally, meaning that we cannot logically explain why it unsettles us. We can find explanations, but since the phenomenon is in itself harmless, it stays irrational. It needs to be relateable. So, for example, if you as an author are scared of buttons it´s not enough to show a button on every page to make someone uncomfortable, since most people aren´t. You need to find the root of your fear and try to convey it to the person reading your story to feel with you. A dark hallway on the other hand has the advantage that it tends to unsettle most people.
This is something you can build upon, in many different ways, making the unsettling scary. A dark hallway, to pick up the example again, is a good place for an attacker to hide. Even if the hallway seems empty, since we cannot see completely, the fear still remains. One possibility is to show or hint at an attacker that actually exists, could be a murderer roaming the house or something supernatural. Even better if said supernatural attacker somehow utilizes the fact that it cannot be seen or uses shadows.
For example: There is a monster in the house that can only move in the dark. Our protagonist sees said dark hallway, unsure if it is there, the eyes fixated on the dark spot where he thinks it might be. He knows that it can´t move forward any further, the light prevents it and his hand is on the switch. But then a small hand-like blurry thing moves over the wall, it seems to sizzle in the light and a faint scream is heard. It moves towards the light bulb and finally crushes it. In the next pages the protagonist retreats further and further into the house in a battle of wits that might or might not be hopeless while said monster is out to get him.
The shock element would be the sight of said monster, it might be in the beginning of the story to help build up tension or in the end as a grand finale, in any way it should be a sight that neither the protagonist nor the reader wants to see again.
And that is how I build up moments in horror stories. Of course I don´t always stick to this, some stories don´t need shock moments at all, some just live off of them, also it really depends on what you understand as unsettling, scary or shocking, of course. But I hope I was able to bring you a bit of insight into how this can work.