6 min read

A scientific guide to the infernal fish of Hades

The denizens of the River Styx have some nightmarish cousins here on Earth.
A scientific guide to the infernal fish of Hades

Hades is my favorite video game of the year, and I’m not alone. Many people have spent the last few hellish months battling their way out of actual Hell as Zagreus, the disillusioned son of Hades. The game’s narrative and its characters are so compelling that every time Zag dies and winds up back in a blood-soaked pool, you’ll want to get up and fail all over again just to reveal another fragment of the story. It helps that every fight makes you stronger and no two are alike, with nearly endless combinations of weapons, power-ups, and “boons” from various Olympian gods to help you annihilate shades and bone monsters on your way to the surface.

There are plenty of reviews out there if you want to learn more about why this game is great, or you could pick it up and see for yourself. But I want to take a moment to explore one particular aspect of Hades I haven’t seen discussed much: the creatures that dwell in the chthonic rivers of the underworld.

I mean, have you seen them? They’re the stuff of actual nightmares, and every time I catch one I want to kill it with fire, except that many of these beasties live in fire, making this a pointless exercise. So instead, I decided to get better acquainted with the hell-spawn of Hades. And after doing some research, I’ve come to a strange realization: Most of these life forms aren’t that otherworldly, after all.

Or put another way, Earth is home to a number of creatures that looked like they portalled in from the darkest depths of the River Styx. Here are a few things I’ve caught in Hades with my infernal Rod of Fishing, along with some real world animals that could absolutely take them in a monster battle.


Ok, I’ll admit this one is kind of cute. But don’t be fooled: The Slavug is hardcore. It dwells in the Phlegethon, a river of fire that overflowed long ago, turning the verdant realm of Asphodel into a barren expanse of rocks and bones.

According to the game, this tough little lava slug spends its days camouflaged in magma and “feasting off of bits of molten minerals, who knows what else.”

While there aren’t any life forms on Earth that can survive a magma bath, there are some impressively heat-tolerant animals living around hydrothermal vents, seafloor geysers that spew up superheated fluids. King among them is the Pompeii worm, a species of polychaete worm that colonizes the walls of hydrothermal vent chimneys, its tail stewing in waters that can reach up to 176 degrees Fahrenheit.

Even more extreme heat tolerance can be found among microbes. Methanopyrus kandleri, a species of archaea that lives near hydrothermal vents, can reproduce at temperatures up to 252 degrees Fahrenheit according to lab experiments. That’s still a far cry from the temperature of lava, but hey, Hell’s a tough environment to show up.

Eating minerals isn’t as strange as it sounds, either. Many deep sea microbes make their own food by tapping the mineral-laden fluids spewing out of hydrothermal vents as a source of energy. And sometimes, these “chemosynthetic” critters will take up residence inside a deep sea animal. Take these giant tube worms, which host chemosynthetic bacteria that enter through the skin, or this extremely metal armor-plated snail that appears to have traded a proper gut for a gland full of bacteria.

The scaly-foot snail. Credit: Hong Kong University of Science and Technology.

Who knows, maybe Slavug’s lava-proof body is infested with some mineral-munching hell-bugs of its own.


While Slavugs are a dime a dozen in the River Phlegethon, you’ve got to be a skilled fisherman to catch the Flameater, a legendary beastie with winding tentacles and a scaly body that Hades’ in-game dialog likens to the Greek mythological dragon-serpent Ladon. The Flameater doesn’t look particularly serpent-like to me, but I found myself at a loss to say what real world animal it does resemble. Deep sea biologist Andrew Thaler, however, had an answer right away.

“The Flameater looks like a dead ringer for a vampire squid,” Thaler wrote in an email.

Wow, it sure does.

Thaler noted that the game’s description of the Flameater—as a beast that “appears to be descended from monstrosities born of the Underworld itself”—also lines up with the vampire squid, whose Latin name, Vampyroteuthis infernalis, literally translates to “Vampire squid from hell.” Despite its demonic look, the vampire squid is a detritivore that floats peacefully through the abyss, deploying sticky filaments to collect and eat tiny particles of organic matter called “marine snow.” Maybe Flameater is also a pacifist, in which case we should all feel very bad for handing him over to Hades’ Head Chef to butcher in exchange for chthonic keys.

A taxonomic aside: The vampire squid is not a squid, nor is it an octopus. It is a unique lineage of cephalopod that occupies its own order, the order Vampyromorphida. To scientists, this suggests it’s some sort of living fossil, but it seems equally likely that Hell itself unleashed this cephalopod-shaped demon.


The Gupp is a common fish that can be caught in the waters surrounding the Temple of Styx. But there’s something quite uncommon about its biology: According to Hades, the little green guy exists “in a state somewhere between life and death.”

There are animals on Earth that straddle the line between life and death, too. Take, for instance, the Alaskan wood frog, which spends about half the year frozen solid beneath decaying leaves before thawing out every spring to breed. While frozen, the animal has no heartbeat.

The hardy little wood frog. Photo Credit: Wikipedia

“In a lot of ways, it’s not a living organism,” Don Larson, a biologist at the University of Alaska who studies these amphibious popsicles, told Alaska Dispatch News last year. Larson’s research suggests that wood frogs survive repeated bouts of freezing by flooding their cells with glucose and other chemicals that act like anti-freeze, helping prevent tissue desiccation.

It’s not clear whether the joyless River Styx is cold enough to host animals with a similar ability. But the real-world Styx—a tiny moon of Pluto—is absolutely glacial, and anything that could survive there would need an unholy level of anti-freeze coursing through its veins.


Found in blood-soaked waters of Tartarus, the Knucklehead is definitely a weirdo. Is it a fish with a human skull, an accursed soul trapped in a fish’s body, or some other nightmare entirely?

Deep sea biologist Nicole Morgan said the Knucklehead reminded her of the barreleye, a bizarre-looking fish with a bulbous, transparent head and tubular eyes capped by bright green lenses. But she admitted it’s “not a perfect match.” Thaler said that the Knucklehead “just looks like a generic fish wearing a human skull.” But he added that Coccosteus decipiens, an ancient placoderm that went extinct hundreds of millions of years ago, also had a heavily armored bony head.

Personally, the Knucklehead reminds me of a chimera, also known as a ghost shark. Here’s some footage of one of these dead-eyed denizens of the deep captured by the Monterey Bay Aquarium Research Institute:

In the real world, chimeras are a diverse group of cartilaginous fish related to sharks. But in Greek mythology, chimeras were literal mashups of different animals. So it kind of makes sense that the Hades version would look even creepier than its abyssal cousin.

This is just a small sampling of the river beasts you can catch in Hades. If you’ve got a favorite hell fish that I haven’t covered, let me know!

Top image: Supergiant Games

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