Adventuring's hard enough — you've got brain-wracking puzzles, hazardous environments (sometimes literally), and, if you're unlucky, the interface itself.
And now, there are monsters that disguise themselves as loot!?
A Chest Monster is an enemy or hazard that has disguised itself to look like something positive: as an ally, a Save Point, or — in the archetypical example — a treasure chest. They are frequently called "mimics" for this reason, and are generally stronger (sometimes much stronger) in battle than the surrounding Mooks in the area. Sometimes they are ordinary chests with a monster locked inside. It may or may not be possible to escape from a Chest Monster once it's been disturbed — you either defeat it, or die trying. For those who can slay these, beating a Chest Monster usually also means they'll drop loot, generally better loot than normal enemies and/or on the same level as a chest.
Obviously, Chest Monsters aren't threatening at all if you can avoid triggering them in the first place, but in games that encourage you to always open every last treasure chest in sight, this is easier said than done. It may or may not be possible to identify a Chest Monster without opening it up and springing the trap — sometimes there may be a minor flaw or difference that allows you to tell them apart from the genuine article; sometimes you can use an item or ability to analyze it and tell if it's real. Other times the placement is a clue — if a power-up is right there in plain sight with no guards or obstacles protecting it, it might be a trap. Or not. If all else fails and there are no clues, you'll just have to find out the hard way and hope it doesn't bite back. Thankfully, some games allow Cutting the Knot by revealing it by shooting the chest.
It makes you wonder; where did these things come from? Did a wizard make them, or have people in the world of Dungeons & Dragons been putting chests in dungeons so long mimics have had time to evolve to fill this niche?
See also Inexplicable Treasure Chests, Inn Security, Luring in Prey.
Subtrope of Luring in Prey and Mimic Species. Compare Poison Mushroom, which is a harmful item disguised as a beneficial one, and Ambushing Enemy, which is an enemy that hides in and/or disguises itself as the scenery (though this trope applies if the monsters have to be dug out of the walls first). May overlap with Treacherous Checkpoint if the monster disguises itself as a Checkpoint or Save Point. The inverse is a Fake Trap, where something in the game is made to look dangerous or threatening, but is actually harmless. Can be seen as a form of Booby Trap.
Not to be confused with Chest Burster. Unrelated to a certain metaphor from the 6th Harry Potter novel. Has nothing to do with breast size.
- Black Clover: Asta and Noelle encounter one in an episode, but, instead of being full of treasure, it's instead full of the monster's internal organs.
- Delicious in Dungeon: Mimics are actually a kind of crab that uses treasure chests both for protection (similar to hermit crabs) and as a way to to surprise prey (i.e. adventurers). Justified in that the setting has had dungeons for long enough that it's become a natural environment type, with its own evolutionary niches. This gets expanded on with the introduction of treasure bugs, the natural predator of mimics that slip in to lay eggs that devour them completely when they hatch. True to their name they resemble common treasures like coins and jewelry but are really insects with paralytic venom.
- Frieren: Beyond Journey's End: A Running Gag throughout the series is Frieren getting fooled by mimics (who look like ordinary treasure chests, but can be magically scanned to reveal their true nature) and having to be saved from being eaten by them.
- Interspecies Reviewers: Mimic succu-girls are a variation of this adapted to using more than one kind of container, as seen in the Adult Toybox with a treasure chest, a gift box, a wardrobe, and the receptionist uses a pot.
- Miss Kobayashi's Dragon Maid: Fafnir's greed is demonstrated in episode 3 when he plays a Dark Souls parody and is killed by a mimic despite Takiya warning him not to grab the chest.
- One Piece:
- The series has this during and episode in the Thriller Bark arc where Nami opens a chest and a surprise zombie pops out.
- Luffy and Nami encounter a little man who, twenty years before, had fallen into a treasure chest and couldn't get out. He tries to invoke this trope to scare people away from his island.
- Pop Team Epic provides a bizarre example◊ — an insect that disguises itself as a Japanese book store franchisee in order to lure in and kill "subculture bitches".
- Rune Soldier Louie: One episode has a short fight scene with the party attacked by a door mimic, as well as a traditional treasure chest mimic.
- Yu-Gi-Oh!: Capsule Monsters: Joey opens a treasure chest in search of valuables, but it contains a Yamatano Dragon Scroll that captures him.
- Magic: The Gathering:
- It has the Mimic card that looks like a chest monster that is a Artifact-Treasure that can turn into a 3/3 Artifact Creature.
- There's also the Dire Mimic, which is disguised as a wardrobe.
"Sometimes the closet is the monster."
- The card game has a reference to this in the form of Dark Mimic LV1 and Dark Mimic LV3, who both look like chests and give the player an extra draw when activated. They even act as a traditional Chest Monster in Yu-Gi-Oh! World Championship Tournament 2008. In the Pyramid in the World of Sunlight, there is occasionally a treasure chest. it will give you GP, a card... or a challenge by Dark Mimic LV1.
- Other cards also allude to this, such as Yaranzo (classic demon in a treasure box) and Stuffed Animal (demon teddy bear), as well as the Man-Eating Treasure Chest.
- Hungry Burger fits this trope as well.
- In Gold Digger, a flashback strip to one of Gina and Britanny's early adventures has them encounter one of these that's actually guarding a treasure (inside itself). Upon finding out after taunting them that they're actually not interested in stealing said treasure because they're adventurer archaeologists and not thieves, the disappointed monster instead challenges them to a contest: they can keep anything they can snatch before it can bring its toothy lid down to bite, fair and square. Of course, Britanny Diggers is a were-cheetah with super speed...
- A real, living chest is one of the servants of The Beast who ambushes Gaston's invading mob in the climax of Beauty and the Beast. Specifically, a guy steps on a carpet that traps and rolls him up, then dumps him into the chest, which closes, licks, and burps.
- Dungeons & Dragons: Honor Among Thieves: The labyrinth of the Highsun Games has chests all over with various weapons inside to help the combatants. Holga discovers to her horror that not all the chests are legit — some are actually Mimics.
- Fighting Fantasy:
- Caverns of the Snow Witch: At one point, you and your traveling companions, Redswift the elf and Stubb the dwarf, come across one of the Snow Witch's treasure chests whose handle is a bronze serpent, and decide to draw lots to decide which one of you would open it. Predictably the chest is booby-trapped, with the serpent handle coming to life upon touch and biting the hand of anyone touching it, causing severe STAMINA damage. However if Redswift draws the shortest straw, his elven intuition warns him of the danger, and he bypasses the trap by pressing a hidden switch instead.
- Beneath Nightmare Castle has an encounter where after you defeat a group of enemy soldiers raiding a town, you then find a wooden crate they brought along with them and are given the option to open or ignore it. Choose the former and it turns out the crate is filled with severed zombified limbs, all of them coming to life to attack you and must be hacked to pieces.
- The Arabian Nights includes "The Tale of the Fisherman and the Djinni", in which a dangerous djinn, trapped in a bottle by King Solomon centuries before, threatens the human who releases it. This is perhaps a borderline instance of the trope, but it makes the basic idea Older Than Print.
- Discworld: While not an enemy of the protagonist, the Luggage from the Discworld novels is still a ravenous Chest Monster. But it does its master's laundry. It is, however, quite harmful to everyone else. It can also be distinguished from, say, the sort of luggage to steal underwear from, by the feet underneath. And the fact that it will, without eyes, look at you in a very unfriendly manner.
- Everybody Loves Large Chests: The main character of the story is a mimic that loves tasty and shiny things.
- The Harry Potter books have this with The Monster Book of Monsters, a Care of Magical Creatures textbook that is actually a furry, sharp-toothed monster itself, and will try to bite the reader if they don't open it the right way.
- KonoSuba: Double-subverted. Kazuma and Aqua encountered a suspicious chest while exploring a dungeon, and to test whether or not it is a monster, Kazuma throws a rock at it. The chest itself is not a monster, but the wall behind the chest is.
- There Is No Epic Loot Here, Only Puns: When Delta succumbs to temptation and takes the option to randomize the guardian of her underwater shortcut, she gets a giant clam full of fake treasure. She's initially scared by its appearance, but it turns out to be rather affectionate. To her, at least. Intruders may find themselves seized and pinned, though since it's Delta's dungeon, not actually eaten.
- Villains by Necessity: Called an "Aydaptor", one nearly devours Arcie. Later it's domesticated with a spell into a pet by the adventuring party following them, to its horror.
- Parodied with the paedophile disguised as a school in Brass Eye.
- In Kishiryu Sentai Ryusoulger, A literal trope called the Mimic Minosaur trapped most of the Ryusoulgers in its dimension. It is one of few Minosaurs that originated from an object.
- According to its promotional Comic Book, Bally's Space Invaders arcade pinball machines are actually Shapeshifting aliens in disguise.
- Trials & Trebuchets: The Keeper of the List of Warlocks, or "Keepsie" is an intelligent Mimic, and a rare friendly example of the trope. They were created with the purpose of keeping a log of all the warlocks who have ever attended Wildcliff.
- Dungeons & Dragons:
- The great-granddaddy of this trope is the mimic, a blobby monster that can imitate any stone or wood item. The artwork in the first edition Monster Manual depicts one in the shape of a chest, setting the mold to be followed in its videogame descendants. Incidentally, it's capable of making anything it touches stick to it as if glued and thereby making sure whoever touches it first is out of the fight. The second edition compounds the problem by adding a variant that can grow to the size of a building, inflicting a Total Party Kill on any group unfortunate enough to enter the "dungeon." (It's common DM practice to have that type pose as a gazebo.) Fifth edition's Fizban Treasury of Dragons describes hoard mimics, specimens who have grown large and skilled enough to pose as entire treasure troves. They usually live symbiotically with dragons with whom they share lairs — the dragon gets a handy decoy and intruder-disposal system, while the mimic gets a steady stream of prey.
- The "bag of devouring" is a fake Bag of Holding that's actually the mouth of an extradimensional predator, which may or may not be asleep.
- The 3rd edition Epic Level Handbook has the living vault which, in addition to containing valuables, is a powerful creature.
- Not truly a member of this trope, but it is implied that Nimicri, a Genius Loci found in the Planescape campaign that is found in the Chamada layer of Gehenna, might actually be related to mimics, possibly one with divine blood.
- 1d4chan calls this type of monster a "Gotcha Monster". More examples are listed here. These types of creatures were very popular in the early days of D&D.
- From the Spelljammer Monstrous Compendium:
- Space Mimics are a variant of common mimics found in Wildspace. They have most of the same physical abilities, but are much more intelligent; they can levitate and cast low-level illusionist spells. Space Mimics are interested in books, scrolls and magic as much as in food, and sometimes barter for both.
- Ontalak Plasmoids are giant ooze creatures that can produce a fibrous covering imitating most common materials. They generally take the appearance of a derelict ship in the Void and wait for a crew to board it for salvage, at which point they attack with their tentacles to devour them. Ontalaks can take other forms on the surface of a planet, such as a ghost ship or a haunted house.
- Tails of Equestria: Mimics hunt by disguising themselves as inviting objects, such as treasure chests, doors and chairs, and waiting for people to come close enough to attack.
- Warhammer Fantasy Roleplay: Shiners are a type of giant amoeba that inhabits damp, dark places such as ruins and spreads itself thin over objects, giving them a shiny, glittering appearance that makes them seem more interesting and valuable than they would otherwise be. When treasure hunters or tomb robbers try to grab a shiner's perch, its shoots gouts of acid at them.
- DSBT InsaniT: This is Kayla's main power, creating treasure chests that contain traps. She can even hide inside of them!
- Adventurers!! makes fun of this, this time by having the monster be bigger than the box it's hiding in.
- Awful Hospital: The Chest Worm, a worm that leaves its chest-like head on the surface while hiding its body underground.
- Awkward Zombie adds a piece of Fridge Logic; if Mimics evolved into the shape of treasure chests, why do people still make treasure chests that look like Mimics?
- Crystal Heroes features a mimic disguised as a toilet.
- Goblins parodies the type of trap monster found in early editions of D&D with the treasure plant, a Man-Eating Plant that baits victims with treasure that it grows, which only idiots ever fall for.
- Kill Six Billion Demons: One of the many traps in Mammon’s nigh-impenetrable vault are entire rooms filled with DND-style treasure chest mimics (though some take different forms), designed explicitly to lure in any greedy adventurers looking for treasure. They can take on many shapes and sizes, including coins. Unfortunately for them, they're kind of stupid; if you leave a room full of mimics alone, they'll eventually copy each other haphazardly until the whole room is filled with copies of one single object.
- Our Little Adventure: One appears and is fought. The way it acts, the color of the speech bubbles and its general appearance suggests it's a minion of the Lady of Fate and Fortune.
- Rusty and Co. follows the adventures of a party of iconic D&D monsters, one of whom is a Mimic whom default form is a chest. And his real name is "Boxford".
- The Shortest Story: Mimics deconstructs it a bit, with evolutionary pressures moving them away from the normal treasure chests.
- SCP Foundation: SCP-6106 is an ambush predator that transforms itself into a text document to eat anyone who reads it. It's currently taking the form of the SCP file describing it.
- One appears in the Adventure Time episode "Dungeon", vomiting treasure when awakened.
- One of these shows up as the Monster of the Week in the Courage the Cowardly Dog episode "Shirley the Medium". When Eustace Bagge receives a suitcase as an inheritance from his deceased brother Horst, he eagerly opens it up expecting to find money inside, only to discover that it contains a strange demonic entity with gigantic, long arms. The "Box Demon" tries to grab Eustace, Muriel, and Courage, eventually succeeding at pulling Eustace inside the box. The episode ends with Eusatace finding himself trapped in a Pocket Dimension filled with a vast sea of money, much to his greedy delight. However, he can't spend any of it.
- The old snake-in-the-can-of-nuts prank is a popular real life example.
- In nature, this trope is known as "aggressive mimicry", the phenomenon where a predatory organism disguises itself as something harmless in order to lure its prey in.
- The Alligator Snapping Turtle lies in wait wiggling its wormlike tongue until a fish comes along and thinks it's about to get lunch. Then it becomes lunch.
- The golden lancehead, a pit viper unique to one island off the Brazilian coast, catches birds by lowering its tail beneath the branch it's coiled on and twitching the tip. Birds approach to investigate the "wriggling grub" and get snatched up by the snake.
- The spider-tailed horned viper, which is native to Iran, uses an even more sophisticated lure; as its name implies, the end of its tail is shaped like a spider, and it completes the disguise by wiggling the tail back and forth so that it looks like a spider skittering around. Insectivorous birds coming to try and nab the "spider" will suddenly find themselves being attacked by a bird-eating snake. Interestingly, the snake only seems to feed on migratory birds, suggesting that birds native to the area have already learned to recognize the difference between it and real spiders.
- The monkfish, a species of flat angler fish that hides in the sea floor buried in the sand. It waves a lure to attract unsuspecting fish, and when the fish gets close enough it jumps out of the sand and gobbles it down.
- The megamouth shark has an iridescent lining and array of photophores inside its mouth, which may resemble a swarm of bio-luminescent zooplankton, attracting plankton-eating krill straight into the shark's maw.
- There is a type of starfish that stands up on the tip of its arms, forming a kind of tent. Small fish will then see it as a convenient hiding spot from predators, sitting right below the starfish's mouth. Also, wading birds of prey such as herons will extend their wings on sunny days, creating pools of shade where they stand in the shallows. Small fish gather to rest in the wings' shadows, or to look for insects that might have fallen from the "overhanging branches".
- There's cases where an octopus is found inside a clam instead of, well, clam flesh. Apparently it doesn't like being found out.
- Some types of wine involve pickling a live viper in a bottle for months. Usually the snake dies but sometimes, it doesn't. There are even instances of snakes coming back to life and biting people who try to open the bottle.
- A popular internet gag involves linking to a source that appears to lead somewhere innocent (or perhaps not so innocent...), only to instead link to Rick Astley's ''Never Going to Give You Up''. The following link is not one such example:  And there is also the similar gag of tricking somebody into going to a Shock Site.
- There are websites out there that are set up to look like they sell vacation packages and give the visitor the option to be paired up with a companion of their age choice, with the age choices all being under 18 years old. These are actually fronts for federal agencies, who use these false websites to catch pedophiles.
- Many illicit file sharing sites will have a download button for the file you want, usually just some hyperlinked text with a bold typeface at best...and often at least one or two large "DOWNLOAD" buttons that are ads in disguise. At best, you just get sidetracked, at worst, you're taken to a page laden with malware.
OH NO! THE TVTROPES PAGE WAS A MONSTER IN DISGUISE! NOW YOU WILL NEVER ESCAPE!