Eldritch horror design: tentacles, eyes, and non-Euclidean geometry done right

Imogen sent me a reference board last August that had forty-three pictures on it and forty-one of them were tentacles. The brief was for a cosmic horror cultist who had seen the thing beneath the lighthouse, and the board was, by her own admission, "everything I think I want." We talked on a Thursday call and I asked the question I ask on roughly every Cthulhu-adjacent commission. What if the painting has no tentacles in it at all? She went quiet for a beat, then said, "Oh. Yeah. Do that." The finished portrait has zero visible tentacles and is the single most-shared piece in my Lovecraftian work folder.

This is a piece about painting eldritch character art without falling into the tentacle pile-up, the eye-cluster cliché, or the "I drew a spiral and called it non-Euclidean" trap. I'm going to walk you through the design decisions I make on cosmic-horror briefs, what to imply rather than show, where eye placement actually matters, and the specific failure modes that turn a Lovecraft commission into a Hot Topic t-shirt. If you've been carrying a cultist, an investigator-turned, a Deep One hybrid, or just a regular person who has seen too much, this is the section of the order form I'd staple a copy of this article to.

Table of contents

• The "what should not be" composition rule
• Why implication beats depiction in cosmic horror
• Tentacles, when they earn their place
• Eye placement: the single most-asked-about choice
• The non-Euclidean visual joke and how to actually do it
• The colour palette of wrong
• Common mistakes in cosmic horror briefs
• Starting a cosmic horror brief

The "what should not be" composition rule

Lovecraft's whole literary trick is that he describes what the narrator cannot describe. The horror lives in the gap between the sentence on the page and the thing the narrator is trying and failing to render. Translating that to paint is harder than it sounds, because painting is a medium that has to render something.

The rule I use on every cosmic-horror brief: the painting needs one piece of geometry that the viewer's eye refuses to lock onto. Not the whole painting. Not a smear. One specific element, rendered with otherwise plausible photographic plausibility, that doesn't quite resolve.

This might be a shoulder line that doesn't connect to where the arm should attach. It might be a doorway behind the figure whose perspective lines disagree with the rest of the room by about four degrees. It might be a sleeve cuff with too many folds to make sense for the wrist inside it. The rest of the painting reads as a portrait. One element reads as a problem.

When the viewer's eye keeps returning to that element trying to make it work, the portrait has done what Lovecraft did on the page. The horror isn't shown. It's the inability to see it cleanly.

Imogen's cultist works because of the bookshelf behind her. The shelf is correctly painted, the books are correctly painted, but one row sits at a perspective that says the wall is curving in a way the rest of the room denies. Nobody who has looked at the painting has spotted it consciously on the first pass. Everyone says the portrait makes them uneasy and they can't say why. That's the rule working.

Why implication beats depiction in cosmic horror

I get this question on roughly every other cosmic-horror brief: can we just show the entity?

The answer is almost always no, and the reason is mechanical rather than artistic. The human visual system is excellent at categorising shapes. If I paint Cthulhu in full view in the centre of the canvas, your brain takes about a quarter-second to file it under "octopus-bat-guy" and then move on. The horror collapses the moment the categorisation completes.

What works instead is composition that asks your eye to keep moving. A figure in the foreground, doing something a normal person would do, with the trace of something else in the painting that your eye registers but can't categorise. The shadow behind the lighthouse keeper that is longer than the lighthouse keeper. The water in the cup the investigator is holding, which has a reflection in it that doesn't match the room. The wallpaper pattern that becomes, on the third pass, almost a face.

Imply, don't depict. Or if you must depict, depict the aftermath of the thing, not the thing itself. Wet boot prints leading up a staircase with no one on it. A coat on a hook that the painter has drawn slightly wrong, like it doesn't quite hang the way a coat hangs. The character with a smile that the painter has placed half a centimetre too high on the face.

This is also why I lean into the atmospheric character art toolkit harder on cosmic horror briefs than on any other genre. Fog, candle flicker, mothlight, smoke — these are the tools that let you not show the thing while making the viewer feel its weight in the room.

Tentacles, when they earn their place

I am not against tentacles. I am against the tentacle pile-up.

A single tentacle, placed precisely, doing one specific job in the composition, is one of the most effective horror elements you can put in a painting. The problem isn't tentacles. The problem is that most cosmic-horror commissions arrive with a reference board that says "more of them, basically." When the painting ships, the tentacles have become decorative — they're a texture, not a threat.

A few rules I've settled on for when tentacles earn their place:

• One tentacle is more frightening than ten. If you see ten tentacles, you understand the creature has tentacles. If you see one, your brain is left to construct the body it's attached to, and the construction is always worse than anything I could paint.
• The tentacle should be doing something specific. Holding a teacup. Resting on a windowsill. Trailing from the cuff of a sleeve that looks otherwise normal. Tentacles in motion read as fight scenes. Tentacles at rest read as horror.
• Skin texture matters more than shape. A tentacle painted with the wet sheen of an octopus reads aquatic. A tentacle painted with the matte dryness of human skin reads wrong on a level the viewer can't articulate. I usually push for the second.
• Hide the join. The single most common amateur mistake is showing exactly where the tentacle attaches to the body. Hide the join under a coat, behind a shoulder, off the edge of the canvas. The viewer's imagination paints the worst version of the connection.

Tomasz commissioned a Deep One hybrid in November last year — a fisherman in late middle age whose hybrid features were supposed to be just starting to show. The reference board had the usual gill-and-tentacle-cluster headshots. We agreed instead on a portrait where the only "wrong" thing visible is the webbing between his thumb and forefinger as he holds a cup of coffee. Nothing else in the painting tells you what he is. Everything else in the painting tells you that he knows what he is. The piece runs as my desktop wallpaper now, and Tomasz reports that one of his players cried at the table when they saw it.

Eye placement: the single most-asked-about choice

Half my cosmic-horror clients want some variant on "extra eyes." This is one of those design decisions where I push back hard at the brief stage, because the difference between an extra eye that works and an extra eye that wrecks the painting is roughly two millimetres of placement.

The bad version: a third eye in the centre of the forehead, between the eyebrows, well-defined, fully open, the same scale as the other two. This reads as a clip-art chakra symbol or a fantasy-novel cover from 1986. The viewer's brain files it instantly under "magic third eye" and the horror is gone.

The good versions:

• An extra eye partially closed, almost asleep, in a place where the skull anatomy makes sense — high on the temple, under the hairline, in the soft tissue near the collarbone. It looks like a feature the character has always had and is not currently aware of.
• An eye that is the wrong scale. A pupil-sized speck on the cheekbone that you only notice on the third look. The brain registers it as a beauty mark first, then has to revise.
• An eye in the iris of one of the existing eyes — a second pupil within the iris, off-axis, suggesting that the eye is looking at two different things.
• An eye reflected in something that shouldn't show a reflection. The character's mug of tea contains an eye looking up out of it.

Placement matters more than count. Adding three more eyes to a face mostly makes it busy. Adding one in the wrong place makes the painting permanent.

I also push back on glow. Glowing eyes in cosmic horror are the visual equivalent of writing "and they were SCARY" in your manuscript. Eyes that hold light strangely — a reflection point one millimetre higher than physics would predict, an iris colour just off the human spectrum, a pupil that's a little too dilated for the lighting — these unsettle without announcing themselves. Same principle I lean on for weird west work, and the Curse of Strahd NPC portrait roadmap walks through how I apply it to vampiric subjects too.

The non-Euclidean visual joke and how to actually do it

"Non-Euclidean geometry" is the phrase clients use when they want the painting to feel impossible. It's also the phrase I most often have to translate, because the literal mathematical idea (geometry where parallel lines diverge or converge) doesn't read on canvas the way clients imagine.

What actually reads as non-Euclidean in painting is this: two reliable spatial cues in the same image that disagree by a small amount.

Some specifics I lean on:

• The room behind the character has two vanishing points that don't quite converge to the same horizon. Subtle. Two or three degrees of disagreement. Enough that if you try to draw the perspective grid back over the painting, the grid won't lock.
• A reflection that's not where the reflection should be. A window reflects the room, but rotated four degrees. A puddle reflects the ceiling, but the ceiling has one more support beam than the actual ceiling.
• A door frame that's slightly trapezoidal in a way you only notice from the bottom. From the top of the canvas it looks rectangular. From the bottom it doesn't.
• A shadow falling at a direction that contradicts the light source by maybe ten degrees. Not the wrong side. Just the wrong angle.

Here's the test: if a viewer can articulate what's wrong with the painting on their first look, the trick has failed. The viewer should feel the painting is off and not be able to point to it for a few minutes. That's the non-Euclidean joke working.

The most common cosmic-horror brief I quietly redirect is the one that asks for "impossible geometry everywhere." Impossible geometry everywhere is just abstract painting. Impossible geometry in one load-bearing place is horror.

The colour palette of wrong

Cosmic horror has a tradition of green, and I mostly avoid it.

The green palette — sodium-lit fog, sickly seaweed-green flesh, glowing yellow-green sigils — is so heavily associated with B-movie Cthulhu that using it instantly drops the painting into pastiche. When a client sends me a reference board full of green-glow Lovecraftian art, I steer toward what I think of as the wrong-warm palette instead.

The wrong-warm palette is mostly browns, ochres, and dull reds, with a single colour element that's wrong for the lighting. A scene lit by a fireplace where the character's pupils have caught a cool blue highlight that no fireplace would produce. An afternoon room with everything warm except for the rim of one of the character's ears, which is sitting in a cool light source that isn't in the painting.

The principle: if the rest of the painting commits to a lighting register, breaking that register in one place breaks the room. Green-glow horror reads as fantasy. Wrong-warm reads as cosmic.

For the unsettling register, I work with the same palette I described in horror character art commissions — Ink shadow, Parchment warm, Crimson as a single load-bearing accent, and a single cool that doesn't belong. The eldritch in the cosmic sense doesn't need its own colour. It needs the wrong colour, used once.

Common mistakes in cosmic horror briefs

This is the section I want every client to read before the kickoff call.

• Too many wrong elements. If everything in the painting is wrong, nothing is wrong. The horror is the contrast between normal and not. A painting where the curtains are wrong, the wallpaper is wrong, the doorway is wrong, and the character has six eyes reads as a busy fantasy illustration. Pick one wrong element and let it do all the work.
• Tentacles as set dressing. Filling background space with tentacles is the cosmic-horror equivalent of filling a fantasy background with random dragons. It reads as theme park.
• Showing the entity in full. If you can identify what the creature is on a one-second look, the horror collapses. I will sometimes paint the creature, but always partial, always partly obscured, always with the viewer's eye left to do the construction.
• Glow. Glowing eyes, glowing runes, glowing tentacle tips. Glow is what fantasy uses to say "magic." Cosmic horror uses absence of light to say the same thing. The thing in the corner of the room isn't lit. The thing isn't visible at all.
• "Madness swirls" in the background. Visual chaos behind the character doesn't communicate madness, it communicates "the painter didn't know what to put back there." A quiet background — a sparse room, a still ocean, an empty corridor — with one wrong element does more.
• Treating Lovecraft as a costume. Robes, tentacle headdresses, fish-people headshots done as straight character portraits. The genre is at its strongest when the character looks normal and the painting feels wrong, not when the character is dressed as a Halloween Cthulhu and the painting feels fine.
• Over-symboling. Yellow signs, Elder Signs, Esoteric Order of Dagon medallions. Used carefully, one of these is a load-bearing prop. Used decoratively, they read as a t-shirt design.

If you want a deeper read on where these principles cross over into 1920s investigator briefs specifically, the Call of Cthulhu 1920s investigator archetype piece works through how I dress and pose period-appropriate figures around the same horror engine.

Starting a cosmic horror brief

If you've been carrying a Mythos character around — a Call of Cthulhu investigator who has just lost a sanity check too many, a Deep One hybrid passing as human, a cultist mid-conversion, an antiquarian who has read the wrong book — the order form is the most direct way to get a brief in front of me. Write "cosmic horror" or "Lovecraftian" in the notes and we'll talk about which of the trick boxes the painting needs to open.

The closest reference for this kind of work in the portfolio is the back half of the recent horror set, where the trick is almost always one wrong element rather than a pile of them. For longer projects — a campaign cast, a Mythos novella, a self-published Cthulhu-adjacent setting — the GM world-building service is the better entry point, because scope conversations belong upstream of the painting. For a single iconic portrait, the character work service covers process and pricing.

A note I include in every Mythos brief, framed plainly. If your commission is fan art of a specific game's named NPC or a Lovecraft-derived figure from a TTRPG line, the painting is personal-use only — not for resale, not for commercial print. The studio handles that conversation the same way we handle it on Strahd commissions, and the character art commission pricing page touches on it briefly. For original Mythos-flavoured characters of your own invention, you own the painting outright.

Either way: write the one-line pitch first. "A lighthouse keeper who has stopped going up the stairs at night" is a brief. "Cthulhu cultist, scary" isn't. The painting starts the moment you can say the sentence and hear the character in it.