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 that are carnivorous and thick-skinned, move very slowly at 3 speed and fight using claw attacks. They come in three different sizes: small, large and giant. 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 or finds it by searching while they are 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.

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.
• 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. 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 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; searching while next to the pet or applying a stethoscope to them will reveal them. 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.

Generation

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

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 while the level difficulty is 9 or higher, there is a ¹⁄₅ chance of a mimic being created in a doorway and disguised as a closed door in place of 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 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 a 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.

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.

Identifying items

Mimics can also be useful for formally and informally identifying various other items:

• 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.

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 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 even weaker roles can defeat mimics this way without taking a single hit.

In those same versions, 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 eating a mimic corpse or tin breaks the conduct.

In NetHack 3.6.0 and earlier versions, including some variants based on those versions, an umber hulk's gaze attack will not uncloak mimics that it targeted—this is fixed in NetHack 3.6.1 via commit b5a027c3.

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.

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

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 ]

Translated from the Russian by Constance Garnett.