Mind flayer

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A mind flayer, h, is a type of monster that appears in NetHack. Mind flayers are omnivorous humanoids with octopus-like tentacled heads, and possess flight, telepathy, see invisible, and infravision. They will also collect gold, gems and any other items they come across. They share a glyph with the dwarf king.

A mind flayer has a weapon attack and three tentacle attacks that can eat its victim's brains - they are also capable of emitting mind blasts that can lock on to you or other monsters on the same level as them: if a monster is either close enough to them or else possesses telepathy, they take d15 damage, which is affected by the half spell damage property. A tame or peaceful mind flayer will not deal damage to you this way unless they are under conflict.

A character that has their brain eaten by a mind flayer's tentacle attack loses intelligence, has their wisdom abused and can also be subjected to amnesia - losing enough intelligence this way causes an irreversibly fatal instadeath by brainlessness, and cannot be averted with life saving or being polymorphed; if you are in explore mode or wizard mode and choose not to die at the prompt that comes up, your intelligence is boosted to 5.[1] Non-mindless monsters that are hit by a brain-sucking tentacle attack take an additional d10 of damage per attack to simulate brain loss.[2]

Eating a mind flayer corpse or tin can either grant telepathy or raise intelligence by 1 point, with an equal probability of each.[3]

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

Mind flayer tentacle attacks no longer cause amnesia, and their glyph color is changed to bright magenta.


Randomly-generated mind flayers are always generated hostile. A mind flayer can grow up into a master mind flayer.

In addition to random generation, mind flayers are notorious for potentially generating within the Gnomish Mines outside of Minetown and Mines' End at level creation. These "minesflayers" are the result of the Mines levels using mkclass to specify that a random humanoid monster should be generated at normal level creation - while this is almost always a dwarf, hobbit or bugbear, mkclass can completely ignore the difficulty of the monster it produces and create a mind flayer (or master mind flayer).

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

If a genocided monster with a pre-grown form (that is not explicitly a baby form) is chosen for the summon nasties monster spell, and that pre-grown form is not also genocided, it will appear in place of the genocided monster. This means that mind flayers can be generated via the spell in place of genocided master mind flayers.


Though they are the weaker of the two flayers, with 5 base AC and fewer tentacle attacks, mind flayers are still a major threat throughout most of the game due to their intelligence-draining attack, both for the loss of level maps and item identities and the outright instadeath they can cause. This makes mind flayers and their 'master' kin common targets for genocide, as well as stellar pets for those who can procure a tame flayer.


If you start sensing waves of psychic energy, that is your cue to farlook and check any h you encounter—a somewhat common YASD is to mistake the mind flayer for an easier-to-kill dwarf king, then march in and promptly have your character's brain eaten. If you have telepathy, blinding yourself temporarily (e.g., via blindfold or towel) can be used to quickly confirm if a flayer is present on a level; dwarves also do not generate randomly inside Gehennom, making detection there more trivial.

Mind flayers have an impressive MR score of 90, and will often resist many forms of magic available to a character; scaring them through other means is a similarly difficult task. Polymorphing, e.g. via polymorph trap, can also produce hostile mind flayers much earlier than they can generate normally.


When fighting mind flayers, avoid melee-range combat if at all possible, especially if you are encumbered and/or have low intelligence - projectiles such as daggers or arrows are among your best resources to consistently deal damage, and in a pinch they may even be worth a charge from a wand of death. Alternately, if your ranged attack options are limited and melee is your only out, consider stoning them or taking other measures to prevent or minimize stat loss (discussed in more detail below).

Mind flayers respect Elbereth, though this will not work in Gehennom, and can also be deterred by standing on a scroll of scare monster. While not as secure as Elbereth due to their 90 MR score, an expensive camera or tooled horn can still frighten off mind flayers. Beware that a fleeing mind flayer may still attack you, although it is much less likely to - additionally, a blinded one will not respect Elbereth. Scaring a mind flayer also does not prevent them from mind blasting you. Cancellation will not affect the mind flayer's brain-sucking attacks even if successful.

Preventing intelligence drain

Wearing any greased helm prevents the mind flayer's tentacles from reaching your brain, but the grease has a 12 chance of wearing off with each attack; a non-greased helm has a 78 chance of preventing each of the mind flayer's tentacle attacks. Mind flayers get multiple attacks per turn, so you should not rely solely on a greased helm, especially if you are unable to kill them quickly. Alternate possibilities include wearing a dunce cap or ring of sustain ability: both items will fix your intelligence stat (either at 6 or its current value) and prevent stat loss, and the dunce cap has a chance of blocking the tentacles as with other helms. A blessed unicorn horn or potion of restore ability can also reverse the stat loss fairly quickly.

Polymorphing into a headless monster will protect you from the intelligence drain attacks, which can mitigate the worst of their threat[4][5] - polymorphing into a normally mindless form will not protect you, since as a comment in the relevant code says, players aren't mindless.[6][7]

Remember that none of these methods will prevent amnesia from a successful brain-sucking, and you are likely to be very forgetful after a fight with a mind flayer —have a means of re-identifying items on hand if possible. As a precaution, you can #name and label one of a particular type of item(s) that you consider vital and/or does not auto-identify itself.

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

In addition to mind flayer attacks no longer causing amnesia, unicorn horns will no longer restore lowered stats.


While the amnesia and instadeath from brain-eating are enough to make both forms of mind flayer a popular target for genocide, do not attempt blessed genocide of mind flayers if you are a dwarf! Using a blessed scroll of genocide will remove all h from the current game including dwarves, serving as a particularly aggravating form of YASD for dwarvish characters. Also, be sure to mind your spelling, especially if you are a Monk—misspelling it as "master mindfalyer" will only parse the word "Master", one of the Monk's rank titles, and wipe out you and all other monks.

You should already try to identify the beatitude of possible scrolls of genocide before reading them if at all possible, and this is especially true if you plan to eliminate mind flayers with one—in addition to the above, that randomly read scroll you just found may be cursed, and the summoned horde of mind flayers will often result in a quick death; even if you can scare them away, their psychic blasts may still overwhelm you. One or two "normal" genocides, either from the uncursed scroll or a throne, should be used instead; the master mind flayer should ideally be targeted first, as regular mind flayers cannot be generated via summon nasties unless they randomly replace an extinct/genocided nasty.

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

If master mind flayers are genocided, mind flayers can appear in their place if the summon nasties monster spell is cast.

As pets

While highly desirable as pets, taming a mind flayer is extremely hard and dangerous due to their monster magic resistance; you may be much better off using a polymorph trap on your current pet.

Tame mind flayers can make quick work of shopkeepers and various tough monsters, and their telepathic outreach will only lock onto and damage hostile monsters - the harmless message it otherwise produces can be hidden with MSGTYPE. However, there are a few monsters that in turn pose a serious threat should a mind flayer attempt to eat their brain:

  • Cockatrices, chickatrices and Medusa will turn a mind flayer to stone if a tentacle attack lands.
  • Jellies have passive attacks that can easily rack up enough damage to kill a hapless mind flayer attacking one.
  • Shapeshifters and green slimes are similarly dangerous: the former may go down quickly, but will polymorph a mind flayer that eats its corpse, while the latter is extremely likely to turn it into another slime.
  • The Riders will instantly kill a mind flayer if one manages to eat their's brain, though the Rider in question still takes the extra "brain loss" damage.[8]

Ochre jellies are a common sight in the late game, especially as a summonable nasty—consider giving your mind flayer any yellow dragon scales (or dragon scale mail) that you happen upon to provide them with valuable acid resistance.

Mind flayers also have a tendency to attract covetous monsters with their psychic blasts: if approaching the goal level of your Quest, the Wizard of Yendor's Tower or one of the many demon lairs of Gehennom, you may want to leave them on another floor temporarily. Alternately, if you intend to draw covetous foes to the stairs this way, be prepared accordingly; in particular, a mind flayer pet or polyform can be used by Rogues on their quest to awaken the Master Assassin, who will then warp to you from his otherwise inaccessible dwelling.

Also, remember that only tame and peaceful mind flayers will generate soothing psychic waves—if you see different messages related to psychic waves, are taking damage from them, and you are not generating conflict, then a hostile mind flayer may be on the level. Be especially careful if your tame mind flayer becomes confused—they will turn those psychic waves on you! This also makes conflict similarly perilous - always equip intelligent humanoid pets with a unicorn horn whenever possible. Additionally, a mind flayer's high monster magic resistance ensures that once they reaches level 15, they will become immune to conflict, and thus no threat to you or your brain matter while you are using conflict.

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

As of commit 2f255560:

The chance of resisting conflict now depends on the player's charisma, the monster's level, and the player's level. Conflict is resisted if rnd(20) > min(19, (ACURR(A_CHA) - mtmp->m_lev + u.ulevel)) - thus, there is always at least a 5% chance of resisting it. Conflict also now requires that the monster see the player, not that the monster be in the player's line of sight. These changes are imported from SporkHack.

Additionally, as of commit 0891ef4e, monsters wearing alchemy smocks now gain acid resistance instead of just poison resistance, allowing for more flexibility in kitting out a tame mind flayer. Mind flayers can also gain intrinsics from eating corpses as well, allowing them to gain cold resistance for dealing with blue jellies.

As of commit 2cad4ece, each individual covetous monster will pick either the upstairs or downstairs to warp to.

As a polymorph form

A mind flayer is a solid monster form for polyself: on top of flight, multiple attacks per turn, 5 base AC and the ability to wear all armor, their brain-eating attack is deadly to nearly anything with a mind.

When eating a monster's brain, you gain d30 nutrition per successful tentacle attack and exercise wisdom, without risk of choking; if your intelligence is below its current maximum (e.g., after your own brain was sucked), it will be increased by d4.[9] The intelligence increase is subject to the normal polymorphed attributes rules, and will be reset when you revert to your normal form.

Naturally, players in mind flayer form face the same dangers as pet mind flayers, including potential death from triggering too many passive attacks. Furthermore, brainsucking a green slime causes delayed sliming, and eating a cockatrice's brain causes both immediate stoning and delayed stoning if the immediate stoning was stopped by an amulet of life saving. Sucking the brains of your race or other mind flayers will count as cannibalism as well, though this does not trigger a penalty for each individual brain-sucking attack[10] - for Monks and vegan or vegetarians players, eating brains will also break those conducts. While you cannot choke directly from eating brains, you can become satiated—you will not receive a warning when oversatiated, and thus run a significant risk of choking from eating anything afterward, which is an instadeath even while polymorphed.


The mind flayer first appears in NetHack 3.1.0. From this version to NetHack 3.4.3, including some variants based on them, the game does not recognize the alternate spelling "mindflayer" when selecting a monster for genocide.


Mind flayers are derived from Dungeons & Dragons, where they appear in all editions, and are also known as illithids; the illithid is considered "Product Identity" by Wizards of the Coast, and as such is not released under its Open Game License. Dungeons & Dragons co-creator Gary Gygax stated that one of his inspirations was the cover painting of the Titus Crow book The Burrowers Beneath by Brian Lumley. The first mention of illithids is found in the first issue of TSR Games' official newsletter The Strategic Review; they were included in the Eldritch Wizardry supplement for the original white box edition of the 1976 Dungeons & Dragons game, where they were depicted as Lawful Evil; they also appear in the first edition's Monster Manual; and the 3rd and 3.5 editions introduce playable illithids.

The illithid is "a super-intelligent, man-shaped creature with four tentacles by its mouth which it uses to strike its prey"; a tentacle that hits penetrates to the brain and draws it forth, allowing the monster to devour it. Its major weapon is the 'mind blast', a short-range wave of "PSI force" which affects each opponent differently based on how intelligent it is, and can induce many ailments from confusion and insanity, up to coma and even death. In-universe, the origins of the illithids are subject to many conflicting stories.

Illithid society is structured around a creature called an "Elder Brain", which lives in a pool of cerebral fluid in the center of a city. Dead illithids have their brain extracted and taken to this pool to have its contents absorbed, which illithids believe a form of immortality; this Brain also functions as a vast library of knowledge that an illithid can call upon with a simple telepathic call. Psionic potential is thus an integral part of the illithid identity, and they typically communicate by projecting thoughts and feelings to each other.

While illithids do have a patron deity known as Ilsensine, few of them actively worship her - both because they believe themselves the most powerful creatures in the universe, and because Ilsensine is more of an "abstract" deity that represents universal knowledge and one’s mastery of their own mind, a state that all illithids seek. Outcast illithids that turn to wizardry are often known to become alhoons.


<The mind flayer>'s tentacles suck you!
A mind flayer has hit you with its brain-sucking attack.
Your brain is eaten!
You lost intelligence and/or memory of items and floors to the brain-sucking attack.
Your <helm> blocks the attack to your head.
Your worn helmet successfully protected you from its tentacle attack.
You don't seem harmed.
You were protected you from the tentacle attack due to being in the form of a headless monster.
Your last thought fades away.
You died of brainlessness.
<Foo>'s brain is eaten!
A monster was hit by a mind flayer attack, and takes an extra d10 damage.
<Foo> doesn't notice.
As above, but the 'victim' was mindless and takes no extra damage.
<Foo>'s last thought fades away...
A monster was killed by the brain-sucking attack.
Ingesting that is fatal.
You ate the brain of a Rider while in mind flayer form, dying instantly and abusing wisdom if you are revived by an amulet of life saving.[11]
You have a sad thought for a moment, then it passes.
A tame mind flayer was turned to stone from an attempt to eat a monster's brain.

Variants and patches

In the Heck² patch, one of the possible special levels in the "heck-a" list is filled with mind flayers.

In the Lethe patch, the Wizard's Manse map for the fifth floor of the Lethe Gorge has a throne room with three thrones, two of which are occupied by sleeping mind flayers - one mind flayer generates with a wand of lightning and the other generates with a wand of sleep.


Mind flayers and their master kin are somewhat different in SLASH'EM - in an unusual reverse of their attack dice from vanilla NetHack, the master mind flayer has three brain-eating attacks, while the normal mind flayer has five. All the more importantly, the ring of free action provides Luck-based protection against their brain-eating attacks, starting at a 12 chance of blocking each individual flay and increasing to a 910 chance at maxed-out Luck.[12] This, in combination with a greased helm, can render them somewhat less of a threat.

While genociding mind flayers is still generally a worthwhile idea, there are more sources of amnesia present such as the potion of amnesia and the migo queen's attacks, so this is not a preventative method against amnesia specifically.

Both mind flayer polyforms are incapable of wearing helmets due to their tentacle placement, but can still wear all other armor. In addition, SLASH'EM makes it so that any additional bite or tentacle attacks that would automatically process and result in death (e.g. by attacking a cockatrice) are simply not used; this does not apply to the weapon attack, so as always be mindful of fighting bare-handed.

In the Lawful Quest, the locked chamber in the middle of the Cloud Bank has a chance of housing mind flayers known as the "Spice Girls": one named Ginger is guaranteed to appear, while two others named Victoria and Emma each have a 45 chance of generating. They may be accompanied by two master mind flayers named Mel B. and Mel C., who each have a 35 chance of being generated. Ginger is generated on top of a fountain and a chest that has a wand of cold with 16 charges; the chest also has a 710 chance of containing an amulet of flying, and a 45 chance of containing a wand of digging, making it a possible boon for sufficiently tough players. If either type of mind flayer is genocided, they will be replaced by random monsters with the same names.

SLASH'EM recognizes the "mindflayer" spelling, so it is okay to genocide "master mindflayer", but a typo like "master mindfalyer" will still wipe out all Monks (including you if you are one).


In dNetHack, mind flayers and their master kin are considered primordials. dNetHack also adds parasitic mind flayers and parasitic master mind flayers as well as alhoons, mind flayers that have turned to lichdom.

The Drow Noble Quest involves infiltrating a colony of mind flayers and retrieving the quest artifact, the Web of the Chosen: there are 16 mind flayers scattered about the goal level at level creation, generally situated around the elder brain guarding the Bell of Opening. The quest artifact's actual owner, A'gone, is locked up in a cell on the edge of the level, with her mind completely gone due to the mind flayers.

Below this point, there are major spoilers for the Anachrononaut role. They can be accessed by selecting the "Role spoiler" tab.

The Anachrononaut quest features mind flayers in a major role.

In the "age before ages", the mind flayers discovered and woshipped an eldritch "nascent thought" known as Ilsensine, and in bringing knowledge of it back to the past they set off a chain of events that caused the end of the world. While the mind flayer empires were overthrown and brought low, the gods of Law discovered Ilsensine and were consumed, followed by the other gods of the heavens - this is why Anachrononauts do not worship gods and cannot make use of altars. In order to change the future and gain a full-scoring ascension, you must gain access to your Quest from your quest leader before she dies, retrieve the Annulus and obtain the Amulet of Yendor, then reach the lawful high altar on the Astral Plane and invoke the Annulus to purge Ilsensine's influence once and for all before ascending as normal.

Mind flayers are one of the many quest monsters: 17 of the randomly generated monsters are mind flayer-related - of those, 18 are mind flayers, 18 are master mind flayers, and the remaining monsters are either umber hulks or brain golems. Mind flayers are among the various H.P. Lovecraft-inspired r'lyehians that can appear as well, with a 17 chance of a r'lyehian generating: mind flayers make up 116 of randomly-generated r'lyehians. Many mind flayers are also generated scattered around the lower filler level(s) of the Quest at level creation. Genocide does not apply to monsters generated in the Quest branch in dNetHack and notdNetHack, meaning that Anachrononauts cannot preemptively remove mind flayers to make their quest easier.


In xNetHack, mind flayers are moved to the aberration monster class represented by {{white|U} - this is done to avert a potential YASD for dwarvish characters using blessed scrolls of genocide, and also solves the problem of minesflayers.


In notdNetHack, in addition to dNetHack details, the Illithanachronounbinder is a role that is flavored as being a mind flayer of whatever starting race you select, possessing both the traits of that race and those of mind flayers - the role's rank title for experience levels 14-17 is "Mind Flayer".

notdNetHack also adds villithids, vampiric mind flayers that are primarily seen on the Illithanachronounbinder quest.


In EvilHack, mind flayers use h in order to differentiate them more easily for dwarven royals. EvilHack also adds alhoons (which are implemented differently from dNetHack) as well as mind flayer larva, which only generate within mind flayer nurseries. Mind flayer larva live in shallow pools and can only reach adulthood by attaching themselves to a victim's face; if a player is attacked this way, they have only one turn to kill or remove the larva before it burrows itself into the player's brain, killing them instantly and turning them into a mind flayer that can be found in any resulting bones.

Mind flayers are also present as a race of monster within the dungeon, referred to as illithids, and can appear as any of the various racial monsters present within, e.g. shopkeepers and player monsters - they are also a playable race. All forms of illithid have psychic resistance that renders them immune to brain-eating attacks, including those from other mind flayers.

Monster stats by variant

Encyclopedia entry

This creature has a humanoid body, tentacles around its covered mouth, and three long fingers on each hand. Mind flayers are telepathic, and love to devour intelligent beings, especially humans. If they hit their victim with a tentacle, the mind flayer will slowly drain it of all intelligence, eventually killing its victim.