Mentioned in various spots in the Bible, the Leviathan is described as a colossal serpentine creature. It is very heavily armored, able to thwart most types of melee weapons, along with some low-velocity projectiles. In addition, it is capable of breathing fire (or acid, depending upon which translation you use), allowing it to pretty badly mess up any human force which dares attack it. As such, it is best described as a "bioweapon"; whenever God wants to mess up some particularly obnoxious unbelievers, He sics the Leviathan on them.

The Question:

Since the Bible et al don't really describe the Leviathan in greater depth than I have already described, my question for you is this: Given these features, what would a God-crafted Leviathan be like physically? A good example of the type of answer I am looking for is @IndigoFenix's answer. It does a pretty good job, but I am still interested to in what the rest of you think.

"Evolutionary pressures" are not a concern; This is the Judeo-Christian God we are talking about; He is omnipotent, and thus doesn't need to mess about with evolution when creating His ultimate bioweapon.

Nota Bene: I realize that there is a similar question out there; however, this is different. That question assumes evolution as a cause, this question assumes that Jehovah created it.

A Final Nota Bene: I am looking for a creature that is biologically feasible. This means that, although supernatural means were involved in its creation, it cannot depend on magic for its continued existence.

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    $\begingroup$ How could these traits realistically be combined in one creature? Because the intelligent designer wanted it. I don't understand what you are asking. $\endgroup$
    – L.Dutch
    Feb 10, 2020 at 3:13
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    $\begingroup$ By realistically combined do you mean "biologically feasible"? Should we treat God like the more common "sufficiently advanced aliens" in that you want a biologically reasonable creature produced by genetic engineering? Or does intelligent design allow for magic? Consider adding the "science-based" tag. $\endgroup$
    – Zxyrra
    Feb 10, 2020 at 4:07
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    $\begingroup$ Even if you make a leviathan species without evolutionary pressures, such pressures might end up killing it. An arbitrarily large sea monster released into an ocean with a limited amount of food will go extinct. Is this creature hand-fed and groomed by God, or is it subject to nature like every other species upon release? $\endgroup$
    – Zxyrra
    Feb 10, 2020 at 4:11
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    $\begingroup$ Simple answer, yes. Serpent-like creatures can be scaled up much further than most creatures without square-cube issues as their shape mitigates self-crushing to a large degree. Scales which are thick enough to stop primitive weapons are also no problem, and the ability to spit acidic stomach acid wouldn't be unheard of either. $\endgroup$
    – Dragongeek
    Feb 10, 2020 at 15:11
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    $\begingroup$ I don’t see why intelligent design and evolution are in conflict. The laws of nature are particularly sophisticated, with very simple interplay giving rise to complexity. Takes a great engineer to design systems of that nature. All evidence points to God as an amazing engineer, capable of generating a world from a single original word spoken roughly 14 billion years ago. $\endgroup$
    – SRM
    Feb 12, 2020 at 2:22

5 Answers 5


A Thermosynthetic Giant

Deep-sea creatures aren't nearly as restricted by the square-cube law as terrestrial ones; as long as they are made of meat the water can support their weight. The biggest problem oceanic giants have is maneuvering and getting enough to eat. So I'd say the easiest way to handle this is to not have them eat at all.

It is hypothetically possible to create an organism that feeds off of heat gradients directly, converting it into chemical energy to use later using microscopic mechanisms conceptually similar to a steam engine. The reason why this never seemed to take off on Earth is that heat is tricky and inefficient to work with on small scales - the heat differential between one small-scale region and another is not very high, so any hypothetical thermosynthetic microbes that may have existed were easily outcompeted by more efficient chemosynthetic and photosynthetic microbes. No successful thermosynthetic microbes means no thermosynthetic multicellular organisms.

But since we're talking about intelligent design, we don't have to worry about that.

For capturing thermal energy, the ideal design is one with a huge difference in the heat levels between one end of the generator and another. A colossal serpent is perfect. It leads a mostly sedentary lifestyle, with one end of its body buried deep in the earth, possibly by drilling into undersea volcanoes. The other end of its body is exposed to the cold water of the deep sea. Using efficient molecular and macroscopic organs along its body that would put our clunky steam engines to shame, it draws boiling water through its internal vessels, capturing every bit of thermal energy and converting it into fat for later use.

It also has loads and loads of DNA repair mechanisms, to keep it from getting cancer despite its immense size and nigh immortality.

Whenever God needs it to terrorize Egyptians, eat Jonah (it has an isolated gas bladder for such a purpose, it can fill it up by gulping air), or just show off, it pulls itself out of the ground, swims around using its stored energy, and then returns to its resting/feeding place when its Job is done.

Fire/acid breath and heavy armor are no problem once you've got the energy problem handled - hard scales can already deflect bullets and harpoons, and fire breath is easy if you ignore evolution, especially with all those lovely volcanic chemicals like sulfur and methane it will be accumulating over its lifespan. It can even incorporate iron into its physiology by absorbing iron sulfide like the scaly-foot snail.

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    $\begingroup$ I very much like this answer, and am thus accepting it. $\endgroup$ Feb 10, 2020 at 12:29
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    $\begingroup$ loved it! Shudder to imagine being on a shoddy vessel, harpoon in hand when the waves part and against the moonlit sea the veritable endless monster eclipses the moon. $\endgroup$
    – Gustavo
    Feb 10, 2020 at 13:55
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    $\begingroup$ When its Job is done got a chuckle out of me $\endgroup$
    – Sarah
    Feb 10, 2020 at 20:02
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    $\begingroup$ If it's reacting CO2 and water into sugar, and oxygen, all it needs to do is siphon that oxygen into its swim bladder and Jonah can breathe indefinitely. Having an oxygen bladder is also handy when it comes time to burn calories. $\endgroup$
    – mm201
    Feb 10, 2020 at 22:31
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    $\begingroup$ @BillThePlatypus All of the elements necessary for life exist in volcanic vents; with the right molecular mechanisms it could assimilate their matter as well as their energy. $\endgroup$ Feb 11, 2020 at 23:16

Actually, it's not that hard at all.

Consider the Basilosarus (which is a proto-whale, despite the name, not a reptile). It is one of the largest known animals to ever exist, and is the largest extinct animal known following the extinction of the dinosaurs (only the modern Blue Whale was larger, at 98 feet compared to 66 feet of the Basilosarus).

Most renders of this animal give it a more serpentine look in the hind region, and it still had two visible hind limbs in the form of smaller flippers to the forelimbs (all modern whales technically have hind limbs though they only exist in the form of vestigial bones. Even snakes still retain limb bones to some extent).

Acid "breath" is easy to duplicate, as the human stomach houses some of the most acidic substances to break down food for digestion. It's entirely possible that your leviathan uses a controlled regurgitation of stomach acids as a defense mechanism against large prey. They were also hunters and would definitely be the "bigger fish" no matter what they ate.

It's reasonable to suggest it evolves to be even larger (the reason whales can get so big is that water is one of the few substances that is at it's densest in liquid form, which means that it's going to support any "mostly water" weight floating in it, allowing animals to by-pass the typical limitations on size that are inflicted by the Square Cubed law (if you double an object's size, you will increase it's mass by 8 times.) This causes all sorts of problems in living animals, as they can't get enough needed elements like Oxygen to satisfy their new mass, nor can they expel that much waste products. To top it all off, their support structures aren't capable of supporting the mass. You can notice the effect of water on your limitations if you've ever been in a pool and got into a dunking fight. You can easily lift your buddies and even some of the ones who are larger than you because the muscles used to move your body are overpowered in a dense surrounding fluid like water.

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    $\begingroup$ For the love of God man, paragraphs! $\endgroup$ Feb 10, 2020 at 20:28
  • $\begingroup$ Can we please edit punctuation away? $\endgroup$
    – kaiser
    Feb 10, 2020 at 23:51
  • $\begingroup$ @kaiser- You can fix grammar with the edit button if you wish, just don't go in wholesale removing lines of text without explanation like this proposed edit: worldbuilding.stackexchange.com/review/suggested-edits/66586 $\endgroup$ Feb 12, 2020 at 22:14

As Absolutely Badass as God Wants

The whole point of leviathan is that it is a symbol of God’s supremacy over nature.

Let us assume that God isn’t going to bend the laws of physics around the Leviathan for the sake of the discussion.

Being an aquatic creature would mean that it wouldn’t have to worry about weight, so it can get really big. It would only be limited by caloric intake and some issues with circulation

Since it’s a custom creature evolutionary pressures aren’t a concern, so it gets the full works for fire breathing, ultra dense muscle, rapid cell healing, hardened scutes and osteoderms.

It’s implied to be reptilian like in Job, so picture a gigantic crocodile or mosasaurus.

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    $\begingroup$ it wouldn’t have to worry about weight I disagree. Why don't blue whales get infinitely large in size? Assuming physics stay the same, internal structures can only get so big before heat becomes an issue - and the square cube law still holds in water. It might be easier to get bigger in water, but there is still a limit imo. $\endgroup$
    – Zxyrra
    Feb 10, 2020 at 4:13
  • $\begingroup$ This creature is going to spend its whole time under water feasting to keep itself alive that its never going to have time to attack humans... $\endgroup$
    – Shadowzee
    Feb 10, 2020 at 4:26
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    $\begingroup$ If we’re assuming ‘god did it’ as the main design principle: Dream up some extremophilic version of the chloroplast (a’la the deep ocean vent ecosystems), then give the damn thing a seawater cooled nuclear pile instead of a stomach. Run cooling ducts through its body filled with ethanol. Rearrange the digestive system so it’s gills capture and digest krill for raw building material. Then it has infinite energy for marauding and simply has to swim to eat. Why would such a thing exist? Who cares? God willed it so. $\endgroup$
    – Joe Bloggs
    Feb 10, 2020 at 8:14

You're a god. You came to this nice planet. It already have large as a log alligators. And snakes. Oh my me what kind of a snake this is.

You take green anaconda or male saltwater crocodile. Take crocodile. Because Egypt. God like those pyramids, they're nice.

All you do, as a god is to give them venom that interact with the brass weapon and "melt it with acid". But god is lazy. He take 6 days and call it a week. So he takes nitrate, which is a "common" thing in Egypt, usually used for mummification.

Make the crocodiles hunt for prey around nitrates storage (or eat "fresh" mummies). Crocodiles don't consume nitrates, but rather store it in their mouths, making it into pulp which they then puke on offending humans. Nitrate corrodes (melts) brass.

Crocodile leather is quite dense so a brass dart, jawelin or hook can not make a lot of harm to it.

Oh, and btw, nitrate is not so good with corroding steel. So that's why there are no more "leviathans"; they were hunted down with better weapons.

  • $\begingroup$ @SEistoopoliticallycorrect where? and of course it is not. YOu write that book, you say that cabbage is a rose and rose is cabagge. $\endgroup$ Mar 23, 2020 at 21:12

The question you’re essentially looking for is, "how can a creature with said attributes realistically survive?" Short answer is, it can't. You can’t just plop down a creature and expect it to survive. Even if it’s capable of surviving, it won’t last long, as it will need to consume a vast amount of energy just to sustain its needs. The creature is not capable of evolving into existence.

That being said, let’s try to pick apart what attributes could stay with the leviathan without it being killed off, using earth oceans as a example.

colossal serpentine creature

This isn’t likely. Its body is so colossal that it will need to eat a vast quantity of food per day, so this would be a death sentence for the creature. As a result, its body will have to become smaller.

it is heavily armored, able to thwart most melee weapons and low velocity projectiles

Now this can be kept, because it provides protection against a wide range of sea creatures. However, strength sometimes equals weight, which further equals slowness, which leads to being more susceptible to being attacked.

capable of breathing fire or acid

Breathing fire is possible, although it would require a lot of force to to be exerted. Breathing acid is more feasible, so removing fire breath and replacing it with acid breath will make the Leviathan much more realistic.


The creature would look pretty different. It will be a smaller, more serpentine like creature that is arguably slower in speed. It will most likely reside deep down in the ocean, in order to justify its armor. Lastly, it will still be able to breath acid as a defense mechanism. With all these changes, human forces would quite easily defeat such a creature, depending on how small it’ll need to become to actually survive its environment.

That being said, I most likely missed some things, and I’ve probably got some things utterly incorrect, so this answer is most likely not the one your looking for.


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