A mimic is a flesh-eating monster that looks like a chest:


In my fictional medieval fantasy world, they cannot shapechange. They have that appearance (and with their mouths and eyes closed, resemble wood-and-metal chests up to a casual inspection).

They usually have a wooden skin texture, and metal-like frames. They also can slightly change their textures and colors (even reproduce polished metal) to better fit in a colony of monsters, or with other chests around them, the origin of the name "mimic".

When a unaware adventurer comes to loot treasure from what appears to be a random chest, it springs and attempts to eat him. Quite successful that strategy is. Usually a human does not have the reflexes to avoid the fatal full-body bite from a mimic.

The monster only attacks if somebody attempts to open its mouth (lid) or attacks it. It can even be carried away and will remain inert.

In writing the origins of said monster, I am between two possible explanations (there could be a third that has already been discarded, that a mad wizard/god created them):

  • Mimics are monsters that evolved to look like chests, because that was effective in getting prey (adventurers and intelligent monsters).

  • People crafted chests to look like monsters (so would-be thieves avoid stealing for fear of being eaten).

Some wealthy merchants and aristocrats keep mimics inside their treasure vaults (or so thieves' legends say) to prey on thieves.

So far both explanations are good for me, in a dark fantasy setting. So, what one is the one with the least assumptions (and less suspension of disbelief), since we discarded "a wizard did it"??? (i.e. MAGIC is not a viable explanation).

Edit, because boldfaced and/or CAPS text is not enough:

There is magic in this world, but only small-fry stuff. No chimaerical creature creation magic is possible. Also, no gods walk the earth or do random stuff like making monsters on a whim. So intelligent design is out.

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    $\begingroup$ you said no magic, but your second option for the origin implies that they derive from object people crafted... how so? not by magic as you want that excluded, is there another way in a medieval world? Unless Im missing something, of the 3 options you kicked already 2 out excluding magic and intelligent design $\endgroup$ Commented Apr 29, 2016 at 16:59
  • $\begingroup$ I am not implying people crafted the mimics. they crafted the chests to look like a naturally-ocurring creature. Just like many other objects. Maybe you are assuming that the fictional world chests came to be just like our Earth, but maybe they did not. $\endgroup$ Commented Apr 29, 2016 at 17:03
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    $\begingroup$ so you mean that the chest as object came to exist just because somebody imitated a monster, like if we took clams as example and all (not just same as it actually happens to be) our "chests" looked like a clam. Makes more sense that way but what would be the reasons of a monster looking like that in first place, its not that that look would have been of any advantage before people knew what a chest was. In that sense you are back to "why they look like that?" unless you say that they just were like that which kind of cuts the first option out $\endgroup$ Commented Apr 29, 2016 at 17:10
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    $\begingroup$ If you make the chests of this parallel world look a little more organic rather than looking like our world strongboxes then you can take inspiration from our seashells as origin and leverage a bit the imitation skills $\endgroup$ Commented Apr 29, 2016 at 17:25
  • $\begingroup$ I think that the most likely way to go would be people made their chests shaped like the creatures. And th creatures wouldn't look quite like cheat from middles ages earth, but they could be roughly the same shape. I will only open chests with the point of my sword. So when it jumps up to bit, plunge that sword down its throat. Crisis averted. $\endgroup$ Commented Apr 29, 2016 at 19:01

10 Answers 10


There is a relatively simple solution to this problem, if you're willing to have mimics which don't necessarily look like traditional chests.

Perhaps in your world there are a variety of large nautiloid creatures. The shells of these creatures are prised by the rich as a works of art. And, once properly modified, as extremely secure containers.

But somewhere in the world, one variety of nautiloid has long since evolved into a land based ambush predator, this is your mimic. In the wild it spends it's time buried in the soil, until it feels pressure on the hatch of its shell, at which point it springs open and strikes. But with the rising popularity of the nautiloid-shell chests, these relatively intelligent predators learn they can catch a good meal by simply leaving themselves exposed.

Some of the very wealthy may then, as suggested in the OP, keep these nautiloid mimics as pets, guard dogs to protect their vaults.

The average thief may be tempted, despite the danger, as the wealthy keep many of their greatest valuables in these chests. But a more skilled thief might be able to distinguish between the shell patterns of the mimic and those of an innocuous container.


Just a quick note, if we assume the shell diameter of this "mimic" is, say, 124 cm, and scale up from a chambered Nautilus, we get a total weight of 360 kg. The fleshy bits are about half the weight, and at 180 kg of living mass, that puts this thing in the size range of a giant squid.


A chest is very purpose built - the chances of a creature randomly resembling a man-made object and serving as our inspiration to create said object is just ... unlikely in the extreme.

Which leaves us with two possible solutions:


It makes some sense for mimics to have evolved to look like chests.

However, there are many different kinds of chests out there!

For mimics to adapt to look like one specific type, it would have to be exposed to those types exclusively over a very long period of time (generations upon generations). And if this is the case, then why didn't some types of mimics evolve to look like beds, or other pieces of furniture which are universally encountered?

I'd also like to point out that chests will most likely be found within people's homes, so what this implies is that mimics spent a lot of time indoors. Again ... how did these mimics come to have such latitude in their living environments? I would imagine that most people would have simply killed those early versions of mimics which snuck into their homes, yet looked grotesquely out of place.

However, if mimics lived outdoors they would simply evolve to look as rocks, since those are abundant in almost any given environment.

So you see, evolution, while it makes sense if you sort of hand wave it through, is still not a good solution.

Unless, of course, many different kind of mimics exist (some which look like rocks, some like chests, others as different kinds of chests, etc.). Additionally, they would have to posses the power to change their appearance to a fairly large degree.

Why, you ask? Because any mimic venturing in a new environment would be identified and killed almost immediately. Unless it has the power to alter itself conciously, based on its surroundings it's going to be stuck in only one environment, with no good explanation as to how they came to look like chests in the first place.

And this is where solution #2 comes in:

Intelligent Design

It makes perfect sense for some twisted genius to create mimics as pets, for fun, or even as a security measure.

You may not wish to have them to be magically created, however there's always the option of breeding them into a certain shape (over time).

For example, some "scientist" (mage, wizard, scholar, merchant, etc) discovers mimics in some far flung place and immediately sees their potential. He brings some back with him, and places them in a dungeon of his own making, which he fills with chests of a certain make and type. Over the course of a few generations the mimics come to look more and more like the chests (or other objects) around them - which was the scientist's objective.

He now places these creatures (which he has trained to not attack him when he simply picks them up) in his treasure vault, where they serve as an added security measure.

If these mimics are widely spread you might argue that he started selling them, or they somehow escaped and started breeding, however at this point they would evolve into other shapes based on their environment.

I would also like to point out that if many people use mimics as a security measure then thieves will simply end up developing a measure to identify them, then simply pilfer the loot from the real chests completely undisturbed by the monsters.


The most realistic approach is to say that many different kinds of mimics exist, and that they have chameleon-like powers which allow them to blend into many environments quickly, rather than slowly evolve to fit into a man-made environment over time (as the people within that environment would find and kill the mimics quickly).

  • $\begingroup$ I won't say that setting has magic, but it does not have magic powerful enough to reshape creatures. If ruling out "a wizard did it" is not enough, let me stress it again in the Q. $\endgroup$ Commented Apr 29, 2016 at 14:34
  • $\begingroup$ I disagree with your unlikely in the extreme assessment. Animals have inspired plenty of creations, like airplanes, boats, pottery, and many other things. No reason why they wouldn't look like neat storage devices if a little more stout. $\endgroup$ Commented Apr 29, 2016 at 19:03
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    $\begingroup$ @XandarTheZenon - inspired, yes. Modeled? Not as such. Do you know many birds the size or shape of a Beoing 747? Many submarines with moving tales such as a whale has? No, because although we might observe a concept (the general shape of a wing), we do not apply that concept the exact same way as the organism in question (with bones and feathers). A chest is a very specific, human storage device. Its design was not derived from something we observed in nature. You're taking a general concept very literally in order to reach your conclusions. $\endgroup$
    – AndreiROM
    Commented Apr 29, 2016 at 19:51
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    $\begingroup$ @AndreiROM Isn't that the point? The OP wants to know if a creature could be like such and such. And as for your example, it is not that relevant. An airplane is very different from a storage device. a teapot shaped exactly like a chicken or a salt shaker shaped like a sparrow are a lot closer to what I'm talking about. Besides, it is not like you'd have to fundamentally change the shape of a squat animal to store things in it as compared to changing a bird shape to make something with an engine fly. You're comparing apples to oranges and saying we can't have tangerines because of it. $\endgroup$ Commented Apr 29, 2016 at 22:18

I'm sorry, I can't meet your requirement for a living creature that can change appearance. BUT how about a found and cultured fungus that can be grown on the inside of a treasure chest. When it sees light, it vents extremely toxic spores or barbed tendrils that ensnare the chest opener.


Naturally evolving to look exactly like a chest, just to lie in wait (potentially for years) for an adventurer to come by, seems unlikely.

A somewhat plausible possibility might be an origin as a creature with some shape-changing abilities (like an octopus has an impressive ability to change its shape, color, and apparent texture in order to blend in to its surroundings). Something which used to hunt vermin like the rats, but would settle into hibernation while disguising itself to blend in with its surroundings - eventually some started getting into cellars or warehouses instead of its more natural cave habitat.

These would have been comparatively small creatures, but some man recognized the possibilities of breeding them to be larger and better mimic certain objects. Eventually he created a breed which was as large as a chest and specialized in just that shape (losing its ability to significantly alter its appearance but more accurately reflecting a chest) and with the habit of remaining dormant for exceedingly long periods of time. Staying in hibernation significantly extends the time needed between feedings (especially as a cold-blooded creature), but a thief trying to pry open its mouth would trigger a basic self-defense response.

Much as dogs were slowly domesticated by learning to live near people and feed off their refuse (which men then bred into everything from a tiny yappy purse dog to an enormous mastiff), men have bred small urbanized grain-sack mimics (wild mimics which moved into the city to feed off abundant vermin in human settlements) to be as big as a chest as a trap for the unwary.


I posit that your Mimics evolved from Giant Clams.
The key evolutionary breakthrough was to extract O2 from the air; if the lungfish could do it, so can the clams! They were already filter feeders; the Mimics merely specialized in filtering out large, too-greedy-to-be-careful-enough morsels. These clams already make pearls, and they're already big enough to hold lots of treasure:
http://www.picionline.org/weblog/wp-content/uploads/2013/11/mareike-clam-fromfile.png enter image description here

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    $\begingroup$ This is pretty close to what I was going to suggest. The logical conclusion: chests are dead mimics. Mimics are common in nature and their "shells" persist after the death of the creature, and so are frequently used as chests. $\endgroup$
    – Willk
    Commented Jan 20, 2020 at 16:09

Making an animals that looks like a treasure chest is not realistic. Even if evolution made this happen, no box maker in his right mind would intentionally design his boxes to look so much like a real world predator that treasure owners could not tell the difference if one snuck into his treasure room. Real treasure boxes would just be redesigned look any way that is different than the mimic.

Intentionally making boxes that look like mimics might be a thing, but then the mimic would never actually capture an adventurer unaware. This would be like designing a box to look like an alligator. Just because the thing isn't moving doesn't mean you'll just stick your hand in and hope for the best.

There are other ways though:

One way to do this is to have a creature with octopus like mimicry skills. Not a bad solution, but if these pests got bad enough, you'd still have that point where box makers would figure out how to design their boxes to look ways that mimics can not by doing things like painting them in patterns or colors that are harder for the mimics to replicate.

In my opinion, the best solution is just to make the monster live inside real boxes. That way, no matter how they are redesigned, the mimics can just slip right into this year's model and go right on ambushing would be adventurers.

Hermit Crab + Coconut Crab = Mimic

Hermit crabs are uniquely adapted to blend into their environment in this fasion. While they evolved to wear snail shells, they show very little discrimination when it comes to putting on man-made objects.

Now imagine a coastal setting where you have particularly large snails like the Australian Trumpet. In this environment, hermit crabs could evolve to be much larger to take advantage of the larger shells. After just a few generations of coexisting with humans, these hermit crabs learn that people make all sorts of useful "shells" like pots, trashcans, and yes: treasure chests.

Your typical, historically accurate treasure room would often have small, high-up, narrow or bared windows that no would be thief could easily get into. This is because treasure rooms were used to store a number of things that a lord would need on a regular basis and you don't want to have to light a candelabra or a gas lamp every time you go in there.

Giant crabs (as seen in the coconut crab) can be remarkably good climbers; so, the height that works well against humans won't necessarily keep them out. When looking for a new shell, your giant hermit crabs know that humans make useful things; so, one could just climb up, turn its body sideways, and go right into these high windows in their search for human stuff to wear. Once inside, they find themselves a nice unlocked chest to call home, and voila! You have a mimic.

As a side note: 90% of the wealth stored in the average medieval treasure room was actually food and trade goods, not gold. This means that these giant hermit crabs would find treasure rooms both a good source of shelter and sustainable food.

enter image description here enter image description here


I think this is more feasible in a natural route than other answers currently suggest...somewhat a combination of the routes you have listed here, naturally evolved, then plucked out to suit our human needs.

Do a google search for Octopus mimic, and you'll find a creature that can mimic several other species...including one you tube video where an octopus appears to mimic a human skull that it's seeing from onlookers watching it. There is no doubt in my mind that you can naturally evolve a creature that finds it's niche in mimic. These mimics are more than capable of adjusting themselves to look like a crab...well enough to draw out a potential 'mate' as prey. If you had a particular species that fed off of hermit crabs...you would then have a mimic creature that changes shape to an unused shell and awaits a crab attempting to use it as a new home for a predatory technique.

Now enter humans...we take one of these creatures and place it next to a waste basket that we throw table scraps into. With a little training (these creatures seem quite intelligent as they can mimic not only what they see, but the behavior of what they see), we let it mimic the garbage bin and start chucking food scraps to it. Oddly enough, I think I just invented an intelligent food waste recycling program. Put them in a room next to chests and continue the training.

I think you want to go with these are creatures that evolved to mimic, that we taught to mimic our treasure chests.


You are set on the word "mimic" but really what you want is a creature/trap that looks like a chest to fill the role of "mimic" from other traditional fantasy settings (or D&D).

I have a solution that can make this work, but it will mean abandoning the chameleon-like nature of the creature/trap.

The creature/trap would perhaps be better as a plant, such as the Venus flytrap

Venus Fly Trap

This would of course, need to be a very large version of this plant. And perhaps with a stronger "shell" that would resemble wood.

Artisans and craftsmen could take these plants, and shape them by carving, and by nailing other bits of wood, and attaching metal bars and beams, locks, and latches - until they looked like chests.

Essentially, these would be plants that have been decorated, masked, or otherwise disguised as chests. And these plants naturally want to eat people. These creatures would be very comfortable simply sitting in the dirt, and it could go well to explain how they can be found hidden in long-forgotten dungeons.

There are certainly no lack of examples from our world of very large plants, of plants that live for a long time, or plants that don't need much sunlight.

A combination of these characteristics, inside a fantasy world, would make this a very plausible and realistic explanation of where these creatures come from.

With a prolific aristocracy, they would be very numerous.


If we are talking realistically the likenesses of a monster evolving creative ways to catch prey is much more feasible. It could be that a shapeshifter decided on just one shape and later evolved to only turn into chests.


So you want chests that eat people? Then let's get rid of the idea that we need shapeshifting creatures. Instead I present to you:

Carnivorous creatures that inhabit chests

They don't need to adjust their look based on the surrounding chests, they simply hop into one of the chests and call it home. This way they can adapt to any human culture, even ones that store stuff in pots or sacks.

They evolved to inhabit hollow trees, crevices, animal dens, etc. and prey on passing animals.

Smaller specimens may even be purposefully introduced into cellars to eat rodents or other pests. They would be safe because a small monster doesn't even try to eat humans, just stays hidden and plays dead when exposed. But they grow bigger over time. If the cellar or a dungeon gets abandoned and no one culls the monsters exceeding a certain size, they might present a threat to adventurers who come there years later.


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