When I decided to write, I knew exactly the genre I would delve into. I wanted to create realities suspended in darkness. Atmospheric and beautifully eerie. Something to make folks shriek and shiver with delight. Unfortunately for me, horror is decidedly a tricky genre to master.
Beside the already daunting task of pulling new ideas out of the abyss, horror often mixes in elements of other genres, making it more palatable for some audiences but also more difficult to pinpoint which elements make it a distinct genre all its own.
At its most basic, horror is defined as an intense feeling of fear, shock or disgust. Word that in any way you like. Terror, dread, revulsion, discomfort, unease. The idea is to scare the pants off the audience. But using individual or universal fears will only get you so far, because let’s face it, I’ve been watching horror for a long time. I have a hole in my soul where terror should live, and I’m probably going to laugh at a lot of what terrifies you.
Does this mean your kind of horror isn’t scary? Not at all, it just means that “scary” is subjective. Which means using “scary” to define horror as a genre is going to leave a few people screaming, “But that’s not horror!”
Oh boy, here we go.
Just because something doesn’t scare you personally doesn’t mean it isn’t scary to someone else. Horror is much more than cheap scare tactics. So how do we reach into the largest portion of our potential audience? Let’s look at it from a different perspective.
If we shift the focus off you, the audience, and focus on our protagonist, then what matters is what your character fears most. After all, this story isn’t about you, is it? Our protagonist is the driving force behind the story. They’re the reason we’re indulging in such a gruesome and unsettling world. What they fear matters. What happens to them matters. Horror is an exercise in empathy, so if we care about our protagonist, we’ll be scared for them. This works a lot better than catering to the individual fears of our audience.
It’s all about that character agency. How does the protagonist react when they are immersed in danger? What decisions will they have to make in order to survive? How do they shape the story around them?
With horror, what really leaves us on the edge of our seat is watching the protagonist lose control in a world where loss of agency means death (or worse).
What makes horror unique is the atmosphere the protagonist is immersed in. Their world is dark, unpredictable, and inhabited by terrible evils/forces bent on destruction. Failure doesn’t only affect the protagonist. Many lives are at stake, chances of success are slim, and the protagonist is our last line of defense. We fear that they will be injured, captured, killed, or faced with a fate worse than death. Once that happens, they are no longer able to progress in the story and all hope is lost. It’s life vs. death, good vs. evil.
Universal fears have their place, too. They use instantly recognizable imagery to exploit what 
Stephen King calls our “phobic pressure points.” Monsters, darkness, isolation, the unknown: these elements challenge our feelings of security. They make us feel alone, vulnerable, helpless. Gore creates a visceral response, reminding us that we are human, we experience pain and face mortality.
Horror makes us face our deepest fears. We want the protagonist to succeed because their success represents our ability to overcome impossible odds, vanquish evil, and live on. It’s the ability to empathize with a character so deeply that we experience fear and distress on their behalf that makes horror truly shine.