Horror aficionados will no doubt be aware of the subgenres expressed through film and literature: survival horror hinges on a lack of resources or an impending disaster; gothic horror focuses on killers or monsters who chase their prey; body horror addresses the grotesque warping of flesh or mutation; and psychological horror deals with shocking mentalities, or deep-rooted trauma. Set apart from these subgenres however – and perhaps one of the most popular genres of horror presently – is cosmic horror, often known as Lovecraftian horror.
Questions not answers
H.P. Lovecraft was a deeply flawed individual – especially concerning his views on race – but his works have endured because his writing style tugs at a reader's curiosity. There are two elements to cosmic horror. First, there must be a curiosity, on the part of the reader, and often also on the part of the protagonist. Both reader and character should ask questions. Second, some of these questions should be unanswered, or possibly unanswerable. Incomprehension and incomprehensibility are trademarks of "cosmic" genres. Finally, because this genre is horrific, at least one of the following should be true: asking questions should be dangerous; the answers provided should be bleak, deadly, or large and uncaring; or the question should be unanswerable but still perceptible. The genre is about asking questions and receiving answers which are partial, dangerous, impossible, or create more questions or any combination of those. With these ideas in mind, let's break down some tools for writing cosmic horror.
Think big picture, write little picture
Cosmic horror is bigger than humanity. The scale of cosmic horror is so massive that humanity is irrelevant – a single human is thus even more insignificant. H.P. Lovecraft's cosmic narratives – for instance Dagon, The Call of Cthulhu, or The Whisperer in Darkness – are all motivated by cosmic currents that pull characters into situations which they cannot avoid, and ultimately cannot change. For this reason, it is important that writers explain the experience of being trapped in these currents, rather than explaining the source or cause of the currents. Describe the character drowning, not the mountain from which the stream flows.
Good cosmic horror does not reveal the big picture except in easily misunderstood or misinterpreted fragments. Instead of lingering on the grand idea behind the narrative, writers should focus in on the minute and disconcerting elements which the characters explore or experience. Rather that the clash of elder gods, cosmic horror is concerned with the dripping, murky, down-to-earth consequences of those clashes.
Lonely
Most of Lovecraft's protagonists were solitary, lonely, and independent. There are a couple of reasons for this. The singular nature of Lovecraft's protagonists serves to isolate their findings – they have no method of presenting cosmic discoveries to the world. Their solitary nature also serves to highlight their lack of agency. Even if they were to understand the cosmic, they find themselves unequipped to change or even survive the cosmic events taking place. The scale of cosmic horror often means that the human race is irrelevant, but readers feel this lack of agency more keenly when presented with a single character striving against this overwhelming force.
Written accounts
Many of Lovecraft's works were presented as written accounts. This is not unique to cosmic horror – Stoker's Dracula is presented similarly – but is a hallmark of Lovecraft's writing style. Further, written accounts give writers access to a wonderful tool of horror: the unreliable narrator. This tool is a favorite of the masters of horror: Bram Stoker's Dracula, Edgar Allan Poe's The Black Cat, and Lovecraft's own At the Mountain of Madness all use this tool to great effect. If the narrator of a story is also a character within the story, then the reader can never be sure that the character is telling them the whole truth of how events unfolded. If the work of fiction is presented as a written account, then the story necessarily has an unreliable narrator. That isn't to say you can't establish an unreliable narrator simply by writing 'in the voice' of a character from the story, but a written account is a useful shortcut to establish that the narrator is not omniscient, and has goals of their own.
Coping mechanisms and insanity
Drug use is prominent in Lovecraft's works, especially opium and morphine – dulling drugs. These are utilized narratively in two ways: they lend to the unreliable narrator trope, and they represent a fall from privilege. The first should be self-explanatory: a narrator under the influence of substances is less trustworthy.
The second narrative use of drugs is a trait unique to Lovecraft's cosmic horror. Lovecraft's protagonists tend to be upper-class and well educated. They are the type of characters who find drug use revolting, or who consider drug use recreational. When these characters turn to drugs as a coping mechanism, rather than a source of enjoyment or despite their opposition to drug use, it demonstrates their deterioration in the face of the horrors they have glimpsed. This is, in turn, linked to insanity: characters in Lovecraft's fiction use drugs to stave off the symptoms of becoming overwhelmed by their own insignificance in the face of the incomprehensible.
Overwhelmed despite preparation
Many horror movies lean on a trope of unpreparedness—the victim of the slasher leaves their keys inside, and has to turn back to retrieve them, giving the killer time to reposition and ambush them. In Lovecraft's work protagonists tend to be educated, well-funded, and intelligent; and yet they are still overwhelmed or undone by the pressures of the cosmic horror engulfing them.
There are two main reasons that Lovecraft's protagonists make mistakes or do the unadvisable: their curiosity gets the better of them, or they lack the agency – despite their preparedness and other meritorious characteristics – to resist the pull of the cosmic event which is central to the narrative. Writers should use whichever of these two seems best able to motivate the story.
If a character is curious, have their curiosity slowly but surely draw them in over their head. If a character is not curious, or if their curiosity cannot overcome their fear, draw the character into further danger to shift the balance between curiosity and fear – either by increasing their curiosity, or temporarily decreasing their fear. To decrease a character's fear, consider having the danger recede or become less visible, or have a more courageous or foolish character lead the protagonist forward.
Everything is horror
The final element which made Lovecraft's work exceptional, was his own personal fear and insecurities. Lovecraft was a man disconcerted by everything – he was reportedly afraid of temperatures below freezing, fat people, old age and a great number of other things. This helped him to find the scary things in everything, but he is famously quoted as saying "The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown." To make use of this quote, I would encourage writers to remember that anything can fill a reader with fear: plants, animals and other mundane elements of the world. Stephen King famously works with the mundane to create fear: imbuing cars with sentience or describing strange behavior in animals. This same approach to horror can be applied to cosmic horror: how is the big-picture cosmic horror causing small-picture changes in reality which the protagonist or other characters can perceive? How can small things become horrific? The main reason is still, as Lovecraft said, rooted in the unknown.
If an animal is behaving strangely, whining to be let inside when it normally enjoys the outdoors: it is not the action that disturbs us – the whining – but rather the inability to determine the reason for the creature's actions: is the dog afraid? Why? Is there something outside which it is seeking to escape, or something inside which it fears will hurt its owner? This is the unknown which Lovecraft is speaking of in the above quote, and this is the unknown that writers of cosmic horror should attempt to evoke.
The ending
Lastly, I want to note that Lovecraft's short stories do not wrap up neatly. Indeed, they often leave loose threads, or even expand into other works. Lovecraft's mythos has entered the public domain, and his creatures can be used by any writer. If you are writing cosmic horror it may be wise to learn from Lovecraft; but be wary of emulating him too exactly. Hints and nods toward Lovecraft's mythos will be appreciated by most fans of cosmic horror, but Lovecraft shouldn't be idealized: he had a flawed personal ideology, he often broke readers' immersion by having characters' written accounts detail things which would not logically be written down, and he had a penchant for telling, rather than showing—a penchant that makes his works read slowly in comparison to similar, modern authors.
So, in ending – take inspiration, but improve upon the source material.