Mimic

The mimic is a monster class that appears in NetHack, and is represented by the lowercase m glyph (m). Mimics are designated internally by the macro S_MIMIC.

The class contains the following monsters:

• m small mimic
• m large mimic
• m giant mimic

Common traits

Mimics are amorphous and unbreathing animals of neutral alignment that are carnivorous and thick-skinned, move very slowly at 3 speed and fight using claw attacks. The three different sizes of mimic - small, large and giant - also act as stages of growth, so a small mimic can grow up into a large mimic and then into a giant mimic.

Large and giant mimics have the ability to stick to the hero, preventing them from moving or using holes or stairs; a hero will become stuck if the mimic hits them with their sticking attack, or else if the hero walks into a concealed mimic, attacks it, or finds it by searching while adjacent. The sticking attack can be protected against with magic cancellation, and a hero in the form of a large or giant mimic can do the same to other monsters that make contact with them.

Mimics are capable of cloaking themselves by imitating items or dungeon features depending on their surroundings—e.g., a mimic in a temple may imitate an altar, while a mimic in a hallway will imitate a boulder, and a mimic in a doorway will imitate a closed door; a cloaked mimic may also appear as a strange object, which uses a right square bracket glyph (]) and resembles a chest in the default tileset (). A hero that polymorphs into a mimic can cloak themselves this way using the #monster extended command.

A cloaked mimic will uncloak if the hero or a monster performs the following actions:

• Walking into a cloaked mimic; this will additionally cause the hero to stick to a large or giant mimic.
• Attacking the cloaked mimic.
• Throwing an item at one.
• Finding it by searching.
• Applying a stethoscope to one.
• Applying an unlocking tool to one while it is disguised as a door - the mimic has a ¹⁄₂ chance of absorbing the tool and adding it to its inventory, which is reduced to ¹⁄₁₀ for artifacts.
• Zapping a wand of secret door detection or the spell of detect unseen while a cloaked mimic is in range.

If an uncloaked mimic is both out of the hero's line of sight for a long enough period, and is not subjected to any other action that would uncloak it (e.g. a pet attacking it), it will disguise itself again. Protection from shape changers will lock a mimic into its base form and prevent it from disguising itself.

Object detection will typically ignore mimics disguised as objects, unless the source is from a cursed potion of object detection.

The following information pertains to an upcoming version (3.7.0). If this version is now released, please verify that the information below is still accurate, then update the page to incorporate it.

Per commit ea0ef81e, attacking a cloaked mimic by with a polearm or lance will no longer result in the hero being stuck unless they are adjacent to the mimic (i.e., they will not become stuck if pounding).

Per commit 29b4c47b, the light from a camera will pass over a mimic impersonating an object, but will uncloak one impersonating furniture - a mimic impersonating some other monster will be woken up without being forced back into mimic shape.

Eating mimics

Eating a mimic's corpse or tin causes the hero to imitate a pile of gold for a short time, unless they have a source of unchanging—a hero that does so while hallucinating will instead mimic an orange. This is considered a weaker form of polymorph, since it breaks the polyselfless conduct and causes the hero to dismount if they are riding, but does not affect the hero's worn armor or other worn items. Mimicking a pile of gold or an orange leaves the hero immobile for 20 turns if they ate a small mimic, 40 if they ate a large mimic, and 50 if they ate a giant mimic. A monster that attempts to pick up an item the hero is disguised as will uncloak the hero, returning them to normal form.

A pet that eats a mimic corpse will temporarily appear as a particular item or monster for the duration of its meal unless the hero has protection from shape changers—as with the hero, this does not affect the pet's worn items, and will force a dismount if they are currently being ridden by the hero. Walking into the pet, searching while next to them, or applying a stethoscope to them will reveal the pet. Of note is that a pet polymorphed into an item while in a shop will be treated as belonging to that shop when using the far look command.

What a monster will turn into when eating a mimic corpse depends on their monster type:

• A little dog may turn into a kitten, and vice versa.
• A dog may turn into a housecat, and vice versa.
• A large dog may turn into a large cat, and vice versa.
• A housecat may turn into a giant rat.
• Any canine may turn into a sink.
• Otherwise, the monster will turn into a tripe ration.

Generation

Randomly generated mimics are always created hostile. A mimic that is randomly generated will appear disguised as an appropriate item or dungeon feature.

In addition to random generation, mimics can be generated in the following circumstances:

• Mimics are commonplace in shops, with a dungeon level-in-100 chance (^DL⁄₁₀₀) of a mimic being generated on an applicable square in the shop at level creation in place of an item. A mimic created in a shop on dungeon level 9 or higher has a 10 × (10 - DL)% chance of appearing as a strange object, and otherwise has a ²⁄₁₇ chance of appearing as a strange object.
• When entering a new dungeon floor that is not the Rogue level, if the level difficulty is 9 or higher there is a ¹⁄₅ chance of a mimic disguised as a closed door being created in a doorway, rather than an actual door.
• The Mimic of the Mines map of Mines' End generates four mimics at level creation, with each one placed atop a set of gems and disguised as one of the four gray stones.
• Three mimics are placed on the home floor of the Rogue quest at level creation, with one of each type placed in one of four random locations where the down stair can appear: they will be generated disguising themselves as said down stair, with the actual down stair placed in the fourth location.

The following information pertains to an upcoming version (3.7.0). If this version is now released, please verify that the information below is still accurate, then update the page to incorporate it.

Per commit 37f6eee1, the "storeroom" themed room contains several chests that each have a ³⁄₄ chance of being a disguised mimic.

Strategy

Mimics are slow but powerful hitters, making them a common cause of death early in the game: as of August 2024, small mimics rank #7 on the list of top death causes on NAO, and all three mimics are ranked within the top 100 causes of death. This most frequently occurs in the form of a hero carelessly bumping into a mimic while shopping, or else underestimating the power of their claw attacks.

Detection

There are multiple methods for a hero to spot and/or uncover a mimic before engaging it in combat:

• An attentive player can usually spot a "strange object" in a shop and distinguish it from the normal glyph for armor ([) or the normal tile for a chest (), allowing them to prepare before uncloaking the mimic—they can also spot a mimic if the monster is imitating an item that is not normally sold in that kind of shop; while it is possible for shops in bones levels to contain off-type wares, this usually becomes apparent upon or before entering (e.g., a ghost is inside the shop).
• Warning reliably reveals the locations of mimics and other hiding monsters within a shop while the hero is outside it.
• Casting a spell of healing or extra healing at a cloaked mimic will produce a distinct message, revealing its presence.
• Intrinsic telepathy will reveal the presence of mimics on the level when the hero blinds themselves, while extrinsic telepathy will also reveal the presence of nearby mimics—if viewed while hallucinating, the mimic will appear as a random monster.

To safely uncloak a mimic in a shop, a hero can throw a single gold piece (via t + 1 + $) down the row or column where they suspect it to be: the gold will be added to store credit and can be picked up later without any trouble. Be sure not to anger the shopkeeper by hitting them with the coin!

Fighting

Despite the danger of a mimic's claw attacks and their sticking abilities, even a low-level or starting hero can dispose of them with careful enough play. A hero can take advantage of the mimic's low speed by using any form of ranged attack against them: even rocks can be sufficient given enough time, and if out of viable projectiles, the hero can lure the mimic away from the pile(s) and run around to retrieve them. An aklys is one of the best options since it can be tethered and thrown repeatedly, and a lance or polearm also works if the hero has one available.

If fighting a mimic in a shop, using certain ranged attacks may not be safe: thrown projectiles will become the shop's property if the shop buys or sells the weapon in question, and while the wand of striking and force bolt spells can work, they also risk breaking fragile items; additionally, using ray-type wands or spells can risk the shopkeeper being hit by the rebound, depending on the shop size.

If a hero ends up stuck to a mimic, they can scare it into letting them go e.g. by engraving Elbereth, which they should have several chances to write successfully due to the mimic's low speed. Once Elbereth is correctly engraved (which you can confirm by near looking with :), rest with . until the mimic flees to avoid smudging it; remember that the hero cannot go down a hole or use stairs while stuck. Scaring tools and other similar items can also scare a mimic into letting go of a hero stuck to it.

Due to the high amount of experience that mimics can give, it is recommended for a hero to be at experience level 3 or higher before dispatching one to maximize their experience gain.

Genocide

Mimics are a surprising candidate for early genocide, outside of emergency genocides where the hero is trying to avoid an untimely death: as mimics are sometimes generated in place of shop items, the idea is that removing mimics from the game will make future shops better-stocked—this rarely makes a significant difference in practice with the exception of Orcus-town, where far more real items are generated in the abandoned shops if all mimics are extinct or genocided.

Other uses for mimics

Mimics can also be useful in formally and informally identifying various items and dealing with certain troublesome scenarios:

• A ring of protection from shape changers can be informally identified by wearing the suspected ring around a known mimic - if the ring is protection from shape changers, it will uncloak them immediately.
• An amulet of unchanging can be identified by wearing the suspected amulet (after testing to ensure it is not cursed) and then eating a mimic corpse or tin - if the amulet is unchanging, the hero will not turn into gold or an orange.
• A hero stuck atop a steed with a cursed saddle can eat a mimic corpse or tin, or feed one to their steed, in order to dismount themselves.

History

The mimic first appears as an individual monster in Hack for PDP-11, which is based on Jay Fenlason's Hack, and is included in the initial bestiary for Hack 1.0—in Hack 1.21, a similar monster known as the faker appears. From Hack for PDP-11 and Hack 1.0 to NetHack 2.3e, the mimic uses the M glyph. NetHack 3.0.0 introduces the monster class and phases out the mimic monster in favor of its three subtypes.

In NetHack 3.4.3 and earlier versions, including some variants based on those versions, the speed system functions differently: the hero and monsters all move at a consistent rate, meaning that an unhasted and unburdened hero character always gets four moves to the mimic's one. This allows for 'hit and run' tactics that can consistently and reliably dispose of mimics with enough care: characters with relatively high starting HP and AC can attack them more safely, and and with skilled play even weaker roles can defeat mimics this way while avoiding damage.

In those same versions, mimics are subject to several bugs and other related fixes:

• Shapeshifting from eating a mimic corpse or tin does not break polyselfless conduct—this is changed in NetHack 3.6.0 via commit 0f0a85d0 so that doing so breaks the conduct.
• Scaring a mimic prints a "turns to flee" message even if the mimic is still cloaked and immobile—this is bug C343-18, and is fixed via commit e84bea20.
• A mimic in a doorway on the Rogue level will mimic a closed door, even though it is not possible for doors of any kind to appear in doorways on that level—this is bug C343-34, and is fixed via commit 1fbd8860. Related to this is bug C343-380, which causes mimics imitating doors to appear on the Rogue level despite being represented with lowercase letters—this is fixed via commit a2257ebb.
• A mimic may disguise itself as a boulder even if they are over a pit or hole, which a boulder would normally fill in—this is bug C343-37, and is addressed via commit 13abd42d and commit 1616f26c so that mimics over pits or holes will not disguise themselves as boulders, and mimics in Sokoban (particularly the giant mimics at the top floor) are much less likely to generate as imitating a boulder if they are randomly placed over a hole or pit.
• A monster uncloaking a hero that is in the form of a cloaked mimic would give insufficient feedback—this is bug C343-191, and is fixed via commit 12586f6e so that an invisible monster marker is placed if the hero cannot see what uncloaked them (i.e. they do not have telepathy).
• A hero in the form of an orange as a result of eating a mimic while hallucinating gets the hallucinatory message for returning to normal, even if the hero's hallucination times out before then—this is part of bug C343-204, and is fixed via commit d8076947 so that the hero's form is changed appropriately when hallucination times out, along with the accompanying message for returning to normal.
• A shapeshifter with polymorphitis that cycles into the form of a mimic does not use the mimic's cloaking ability—this is bug C343-254, and is fixed via commit c2a3a3a3.
• A concealed mimic in circumstances where an action should reveal it (e.g. probing, kicking or applying a stethoscope) is not properly revealed—this is bug C343-366, and is fixed via commit 2cbc40ca and commit 0def692d. Related to this is bug SC343-17, which is fixed via commit b8a51d36 to ensure that a concealed mimic is properly uncloaked by a stethoscope.
• A mimic posing as a statue is described as a giant ant statue when looked at, regardless of the actual statue it is imitating—this is bug C343-375, and is fixed via commit 71219bf0 by adding an extra field that tracks exactly what type of statue or corpse the mimic is disguised as, as well as making them choose a random monster type. This also means that a mimic disguising itself as a corpse can pick a type of monster that is normally corpseless—this is fixed in NetHack 3.6.2 via commit cd6b5ef9.
• A hero in the form of a cloaked mimic can remain stuck to a monster after returning to normal form—this is bug C343-375, and is fixed via commit 121b9e97, which also prevents sticking from occurring at all with small mimics.
• If a pet mimic that is cloaked or a hero in the form of a cloaked mimic is polymorphed into a non-mimic monster, they are not uncloaked—this is bug C343-391, and is fixed via commit ad1dec07.
• Attempting to unlock a door that is actually a mimic acts as though the action is directed at an empty doorway or an open door, and the mimic is not uncloaked since it does not recognize that a monster is present in the doorway at all—this is bug C343-409, and is fixed via commit 1dcaa162 (from GruntHack) so that performing this action uncloaks the mimic. Related to this is bug C343-410, which allows the locked door of the Sokoban zoo to be unlocked even if a mimic (which will be disguised as a boulder) also occupies the square, and the mimic will not wake up if this occurs—this is fixed via commit e379b245 and commit 3b6c59c7, which makes it so that mimics properly imitate closed doors if generated in Sokoban doorways, and will also uncloak if the hero attempts to unlock them; it also fixes a bug that leaves a stale pointer when moving a mimic from atop a hole in Sokoban.
• Performing certain actions towards a doorway occupied by a concealed mimic will not update the map with the unseen monster glyph (if blind) or reveal the mimic—this is bug C343-413. The same occurs when using the untrap command in the direction of a known trap square covered by a concealed mimic, which is bug C343-392. Both are fixed via commit ad1dec07 so that the mimic is properly uncloaked in both cases.

In NetHack 3.6.0 and earlier versions, an umber hulk's gaze attack will not uncloak mimics that it targets—this is fixed in NetHack 3.6.1 via commit b5a027c3.

Origin

The mimic is a type of creature originates from Dungeons & Dragons, where it makes its debut in the 1st edition Advanced Dungeons & Dragons Monster Manual: its hit dice and other traits in NetHack are adapted from this appearance. The mimic has since become an incredibly popular inclusion in other fantasy-based media.

A mimic is a subterranean creature that dislikes sunlight and can change its shape: it can alter its rough, granite-like gray skin to convincingly or even perfectly mimic the appearance and textures of wood, stone, metal, and other basic materials, and can imitate nearly any appropriate object provided it maintains the same volume; to attract prey, it will often take the form of an inanimate object that is most likely to be desirable, commonly including treasure chests. A mimic's skin is covered with light-sensitive eyespots that can detect heat out to a range of 90 feet (27 meters), but are quickly overwhelmed when exposed to bright lights and can even be rendered "blind".

Mimics move about constantly in search of prey, using a powerful adhesive secretion to traverse walls, ceilings and floors alike. Once disguised, the mimic remains completely still and waits until prey makes contact with it, then uses the adhesive to trap them in place before attacking and further restraining them with its strong pseudopods; the adhesive can be weakened by the application of alcohol, and is completely neutralized soon after a mimic dies. A mimic is typically a solitary hunter, though they usually share vast territories with other beings, and a meal of one or two humanoids can sustain them for several weeks.

There are several subspecies of mimics introduced throughout the many editions of Dungeons & Dragons and other fantasy media that it appears in, and they roughly divided into two groups: the "killer mimic" is larger and more aggressive, but less intelligent, and will attack anything that approaches it, while the "common mimic" is smaller but more cunning, and can both use refined combat tactics and use language to negotiate or bargain. The mimics of NetHack are patterned after the former type, though they also possess the common mimic's ability to disguise themselves as more ornate furnishings. A common mimic has their own language and can speak the languages of nearby communities as well, and is known to sometimes offer information or safe passage through their territory in exchange for food.

Messages

Wait! That's <a mimic>!

You walked onto a square where a mimic was imitating an item, causing large and giant mimics to stick to you.

The <item> seems a more vivid <color> than before.

A mimic was healed by a spell of healing or extra healing while cloaked.

Wait, <foo>! That's a <polyform> named <player>!

A monster attempted to walk onto your square while you are in the form of a mimic and have disguised yourself using the #monster command.

Wait, <foo>! That <item> is really a <role> named <player>!

As above, but the monster attempted to pick up the item you were disguised as.

The guard turns around and leaves, puzzled.

A guard entered a vault while you were inside and disguised as a pile of gold from eating a mimic corpse, causing them to leave immediately.

"Hey! Who left that orange in here?"

As above, but you were hallucinating and instead disguised as an orange.

Variants

Variants of NetHack do not often add new types of mimic.

UnNetHack

In UnNetHack, mimics found on a maze level are more likely to mimic a statue compared to other mimics.

dNetHack

In dNetHack, notdNetHack and notnotdNetHack, the Cerulean Sign and Elder Sign are wards that can scare off mimics.

SpliceHack

SpliceHack adds one new monster to the monster class:

• m killer mimic

Encyclopedia entry

Mimic

The ancestors of the modern day chameleon, these creatures can assume the form of anything in their surroundings. They may assume the shape of objects or dungeon features. Unlike the chameleon though, which assumes the shape of another creature and goes in hunt of food, the mimic waits patiently for its meals to come in search of it.

Strange object

This entry is translated from the original Russian by Constance Garnett:

He walked for some time through a long narrow corridor without finding anyone and was just going to call out, when suddenly in a dark corner between an old cupboard and the door he caught sight of a strange object which seemed to be alive.

[ Crime and Punishment, by Fyodor Dostoevsky ]