Common words could be 'monster', 'blood', and 'creepy'. Monsters are classic elements in horror, whether they are werewolves, vampires or some other terrifying creatures. Blood can be a sign of violence and danger. Creepy describes the feeling that horror stories often give, like something is not right and makes your skin crawl.
Words like 'gloom' and 'shadows' can enhance the atmosphere. The word 'gloom' gives a feeling of general sadness and heaviness, which suits the often - doom - laden nature of horror. 'Shadows' can be used to create mystery. For example, a shadow moving on its own can be very scary.
Words related to death, like 'corpse' or 'grave', create a sense of finality and doom, which is a big part of the horror atmosphere. Also, words like 'cursed' give the idea of something being doomed or having an evil power over it. The use of such words makes the reader feel a sense of dread and unease, as if they are in a world full of things that are not normal and are potentially dangerous.
One word could be 'nightmarish'. It's like the story is a nightmare come to life. It can involve all sorts of terrifying and surreal elements. Another useful word is 'unnerving'. It takes away your sense of comfort and security. And 'dreadful' which simply means full of dread or great fear.
Grim, because it gives a sense of being very dark and unpleasant. Macabre, which implies a fascination with death and the grotesque. Eerie, as it creates a feeling of unease and strangeness.
Terrifying, spine - chilling, and macabre are good words to describe a horror story. 'Terrifying' emphasizes the extreme fear it can induce. 'Spine - chilling' gives the sense that it makes your back shiver, like a cold feeling running down your spine. 'Macabre' is more about the grotesque and disturbing elements often found in horror stories.
There are also 'draw and straw'. 'Draw' rhymes with 'horror' and'straw' rhymes with'story'. In a horror story, perhaps there could be a scene where a character has to draw straws to decide their fate, which shows how these rhyming words can be imaginatively connected to the concept of a horror story.