Last Updated on January 22, 2023
Bred by the mind flayers to serve as guard dogs and roving hunters, Intellect Devourers might be one of the scariest monsters in all of Dungeons & Dragons 5e.
Whether it’s their ability to put the most stalwart hero into a permanent vegetative state or the fact they can then consume their victim’s brain, teleport into their empty skull, and pilot them around like the little alien from Men in Black, any player who doesn’t get a cold shiver down their spine when an intellect devourer enters the initiative order clearly hasn’t fought one before.
Today, we’re going to be looking at what is probably the only CR 2 monster that can — given the element of surprise — make a 20th-level adventurer seriously sweat.
We’re going to go into what intellect devourers are, where they live, how to fight them and counteract their abilities, and how dungeon masters can use them to great effect if they want to bring a touch of Alien to the Forgotten Realms.
What Is an Intellect Devourer?
Small aberrations created by the mind flayers, intellect devourers resemble human brains covered in a crusty, sticky chitin that move around on four clawed legs.
They feed on the intelligence of other life forms, taking over their victims’ bodies and puppeteering them to further the dark goals of their illithid masters.
Tiny Aberration, Lawful Evil
Armor Class 12
Hit Points 21 (6d4 + 6)
Speed 40 ft.
STR 6 (-2)
DEX 14 (+2)
CON 13 (+1)
INT 12 (+1)
WIS 11 (+0)
CHA 10 (+0)
Skills: Perception +2, Stealth +4
Damage Resistances: Bludgeoning, Piercing, and Slashing from Nonmagical Attacks
Condition Immunities: Blinded
Senses: Blindsight 60 ft. (blind beyond this radius), Passive Perception 12
Languages: Deep Speech (understands but can’t speak), Telepathy 60 ft.
Challenge: 2 (450 XP)
Proficiency Bonus: +2
Detect Sentience: Intellect devourers have the ability to sense the presence and exact location of any creature with an Intelligence of 3 or higher within 300 feet of it. This ability penetrates all barriers, unless the creature is protected by a mind blank spell.
Multiattack: The intellect devourer makes one attack with its claws and uses Devour Intellect.
Claws: Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) slashing damage.
Devour Intellect: The intellect devourer targets one creature it can see within 10 feet of it that has a brain, forcing the target creature to make a DC 12 Intelligence saving throw, taking 11 (2d10) psychic damage on a failure.
Also, if the target fails its saving throw, roll 3d6: If the total equals or exceeds the target’s Intelligence score, the creature’s intelligence score is reduced to 0. This stuns the target until it regains at least one point of Intelligence.
Body Thief: The intellect devourer initiates an Intelligence contest with an incapacitated humanoid within 5 feet of it that isn’t protected by protection from evil and good. If it wins the contest, the intellect devourer magically consumes the target’s brain.
Also, as part of this action, the intellect devourer teleports into the target’s skull and takes control of the target’s body, killing it in the process.
While inside a creature, the intellect devourer has total cover against attacks and other effects originating outside its host.
The intellect devourer retains its Intelligence, Wisdom, and Charisma scores as well as its understanding of Deep Speech, its telepathy, and its traits. It otherwise adopts the target’s statistics.
It knows everything the creature knew, including spells and languages.
If the host body dies, the intellect devourer must leave it. A protection-from-evil-and-good spell cast on the body drives the intellect devourer out.
The intellect devourer is also forced out if the target regains its devoured brain by means of a wish.
By spending 5 feet of its movement, the intellect devourer can voluntarily leave the body, teleporting to the nearest unoccupied space within 5 feet of it. The body then dies, unless its brain is restored within 1 round.
I really cannot overstate just how scared you should be of intellect devourers.
In terms of design, they’re one of the few monsters in D&D 5e that retains a large amount of their nasty, save-or-suck old-school D&D flavor.
Most of those more brutal monster mechanics from the 1980s (like powerful undead draining your levels whenever they touch you or venomous snakes that just straight up kill you if you fail a poison save) have been toned down for 5e.
Other than crazy high-level magic, it’s virtually impossible to go from healthy to dead without seeing it coming.
Even the Shadow (another classic low-CR monster that punches waaay above its advertised weight) only leeches Strength and only does so temporarily in 5e.
Intellect devourers, on the other hand, are absolute nightmare fuel. Let’s break it down.
First, they know exactly where you are. They can smell your brain from up to 300 feet away, meaning surprise is pretty much off the table unless you have access to the 8th-level Mind Blank spell.
They’re also not mindless creatures.
As you might expect for a brain on legs, intellect devourers are far from stupid, meaning they’re more than capable of using their telepathy to coordinate with one another, set up an ambush, and absolutely ruin your day.
A +4 bonus to Stealth doesn’t hurt either.
Also, this is assuming the intellect devourer isn’t already riding around in the body of someone you know, a local figure of authority, a powerful warrior, or a wizard (they learn all the wizard’s spells).
As with any identity-theft monster (like a doppelganger or an oni), intellect devourers are not only horrifying to fight, but they excel at misdirection and turning people against one another.
So, whether or not the intellect devourers surprise you, there’s virtually no chance you’ll surprise it.
When a fight doesn break out, they’re smart enough to target low-Intelligence PCs first, which is where the one-two punch of Devour Intellect and Body Thief is absolutely brutal.
A DC 12 Intelligence saving throw isn’t necessarily easy for a barbarian, fighter, or other class that — until this exact moment — thought a good Intelligence score was unnecessary wizard nonsense.
Also, that’s not something that goes away when you level up because their nastiest attack is tied to an Intelligence saving throw, and odds are that a 20th-level barbarian is going to have exactly the same Intelligence score as they did at 1st level, and it’s probably not going to be very high.
That means a player character can be dropped to 0 Intelligence (functionally rendering them dead unless someone has a spell like Greater Restoration on hand) on the first turn of combat.
Then the devourer teleports into their head (which doesn’t technically need the target to have had its intellect devoured; it’s just the best way a solo intellect devourer can incapacitate an opponent) on round two and can start using its new meat puppet to murder your party on round three.
Now, the biggest weakness of an intellect devourer is the fact it’s squishy — just a 21 hp brain on legs with an atrocious armor class.
Hit one, and it’s probably going to die — provided you’ve got a magic weapon or are using a spell to overcome its resistance to bludgeoning, piercing, and slashing damage, of course.
This makes setting up and completing the multi-round combo of Devour Intellect and Body Thief hard for the devourer to pull off against a group of enemies.
Obviously, even getting the first half of its abilities off before dying is effectively curtains for a member of a low-level adventuring party.
Getting a character’s Intelligence score back up from 0 is the kind of thing you need a Greater Restoration spell for (hardly a small matter for a gang of low-level rat catchers), let alone restoring the devoured brain of a PC.
This all lends itself to the question…
How Do You Beat an Intellect Devourer?
Simple: Stay out of the Underdark.
Okay, fine. Sometimes the underdark (or the Astral Sea, or anywhere else that Mind Flayers like to show up and ruin people’s days) is unavoidable.
If your party finds itself facing off against intellect devourers, the simplest way to safeguard yourselves is to use the spell Protection from Evil and Good.
This 1st-level abjuration spell guards the target against attacks, possession, and mind-addling effects originating from aberrations, celestials, elementals, fey, fiends, and undead.
Also, if someone in your party does happen to fall victim to the Devoured Intellect or even Body Thief, the Greater Restoration spell, Wish, or True Resurrection will get them back up again in no time.
Obviously, if you’re not a high-enough level to cast the spell yourself, you’re going to need to find a large temple or a cleric powerful enough to help you out.
The best way to deal with this problem is to make sure your sight lines are clear, that you have AoE damage spells like Spirit Guardians or Fireball prepared, and to bring plenty of hirelings with you to act as cannon fodder.
Also, stay together if possible, and make liberal use of any ability or spell (like the cleric cantrip Resistance) to keep your Intelligence saving throws as high as they can be.
Where Do Intellect Devourers Come From?
Intellect devourers first appeared in 1e AD&D, where they were one of the first two monsters (no prizes for guessing the other one) to get psionic abilities.
In D&D 5e, intellect devourers are explicitly the creation of mind flayers — along with most of the other awful stuff that lives in the underdark — and are often used by Illithids as guard dogs or hunters.
A mind flayer with a single intellect devourer as a pet is basically safe from enemy ambushers thanks to the creature’s Detect Sentience; a mind flayer with a whole pack of them is even more nightmarish.
Mind flayers may also send out their intellect devourers inside the bodies of other humanoids to lure others back to their lairs — thus securing the Illithid a steady supply of brains for consumption and research.
DM’s Corner: How Do You Run an Encounter With Intellect Devourers?
Intellect devourers are a definite favorite of mine — not just because I’ve always had a soft spot for mind flayers and everything that comes with them since I played Night Below.
They have this slightly goofy but undeniably horrifying aesthetic that feels wonderfully retro, like Harry Housen and John Carpenter got hammered on malt liquor and started messing around with modeling clay.
There’s a beautiful moment when you run intellect devourers for the first time against a new group of players when they inevitably go from “that thing looks stupid” (or, in the most recent group I did this for “Awww, a brain doggy! Gee, can I keep him?”) to “AAaaooorrghNoooooRunrunrunrun Run Awaaayyy!!!” — usually in a matter of seconds.
That being said, as fun as it is to terrorize your players with intellect devourers, the sheer lethality of this monster means that if you want to deploy it in your game, you’re going to have to be careful.
While being a dungeon master can be about challenging and terrorizing your players, your goal should never be to kill them. If you wanted to do that, Tiamat could just descend from the heavens, jaws agape. Problem solved.
I personally have a rule when I make encounters: the more dangerous something is, the more consciously the players have to choose to deal with it.
It’s fine if the players are ambushed by goblins and need to fight their way out, but if they find themselves at 5th level fighting an adult shadow dragon, you’d better believe it’s on them. Someone messed up, and it wasn’t me.
Despite their low CR, intellect devourers are the kind of monster that can very easily end a PC’s career in a single round of combat.
As such, it’s really important to telegraph their presence, drop plenty of clues about what happens when you let one get too close to you, and generally cover your ass in case your players decide to blame you for the subsequent TPK.
Step One: Hint at Its Abilities
Let the players hear rumors of people acting strangely or encounter an NPC whose personality has totally changed since the last time they met.
Bonus points if there’s a telepathic PC who hears that NPC suddenly thinking in Deep Speech.
They should hear stories of people going missing for a few days and maybe even be hired to find them.
Then, the missing NPC should show up again, different somehow, but also impossible to really catch out as an imposter (they know everything the NPC knew, of course) and very keen to take the PCs into the local sewers to show them “something neat.”
Then, the PCs should find more compelling evidence: a braindead villager, a corpse with no brain, or little clawed footprints. Make the area look like a set from the sequel to Bad Taste.
Lastly, when a fight does break out, I would make sure that there’s a friendly NPC nearby for the devourers to brain drain/body puppet first.
Make every possible effort to show the players exactly how an intellect devourer works and how dangerous their abilities can be while also offering up an opportunity for escape.
If the players choose to stay or run but come back again later, they should have no one to blame for their deaths (and subsequent careers as a mind flayer’s dog’s meat puppet) than themselves.
Adventures With Intellect Devourers
Expedition to the Barrier Peaks: The third adventure in the notorious S series (S1 being the Tomb of Horrors), Expedition to the Barrier Peaks was written in spits and spurts by Gary Gygax and officially released as a published module in February of 1980.
The adventure, which has players descending level by level through a mountain-sized ancient alien spaceship, was the first real introduction of science-fantasy elements to D&D.
It’s honestly kind of a wacky time, full of ray guns, tentacled space monstrosities and — most germane to today’s article — intellect devourers.
If you’re after a seriously gonzo old-school D&D experience, this is a contender for the most quintessentially weird classic D&D adventure outside of White Plume Mountain.
You can buy the original pdf of Expedition to the Barrier Peaks from the DM’s Guild for, like, no money at all.
However, if you’re not comfortable doing conversions from BX/AD&D to 5e, the folks at Goodman Games sell a converted and expanded version of the module as part of their Reincarnated series.
Dungeon of the Mad Mage: A more modern adventure that also involves a weird descent through a giant mountain dungeon, Waterdeep: Dungeon of the Mad Mage is a 5e adventure that follows on from the events of Waterdeep: Dragon Heist and focuses on the megadungeon of Undermountain beneath the city of Waterdeep and the mad wizard Halaster Blackcloak who dwells there.
Halaster stocks his megadungeon with all manner of strange entities poached from throughout the multiverse, including mind flayers and their pet intellect devourers.
Step Two: Hit ’em Hard
The nice thing about using a creature as bizarre and deadly as an intellect devourer (assuming you followed step one and telegraphed the bejesus out of it) is that you can use them to take the wind right out of a cocky party’s sails.
Have the devourers’ mind-flayer master open the fight with a psychic blast, and then launch straight into a round of lethal brain thievery against any PCs who are stunned.
Have a possessed NPC lure away the PCs one by one to be brain swapped.
I’ve only ever pulled this off once, but I basically took the player outside and told them, “Hey, you’re an intellect devourer with all your character’s memories. I can take over your character or you can roleplay as the devourer now and try to take out the rest of the party.”
They were really, really (scarily, even) into it and ended up luring away half the party before the survivors cottoned on.
I also love these kinds of old-school, save-or-suck monsters because, by and large, 5e handles player characters with pretty delicate kid gloves.
Death saves, resurrection, big pools of hit points, bounded accuracy, and the action economy all mean that player characters don’t tend to die unless mistakes are made or the DM is being a real wangrod about things.
This is usually fine for the kind of high-fantasy epics I want to portray in 5e. But sometimes you yearn for a darker, more brutal tone.
Introducing (with the players’ knowledge and consent that the campaign is going to be more lethal than usual and following step one above) intellect devourers immediately makes your game genuinely lethal.
If you want to run a tougher, grittier, more dangerous campaign filled with monsters that punch above their CR, this is the place to start.
Also, if you want that sort of effect but don’t want to do intellect devourers, just steal and rehash the mechanic.
What about a ghost or spirit that permanently possesses people? Swap out the Intelligence saves for Wisdom or Charisma and the brain drain for, like, a soul burn, and you’ve immediately got a more terrifying, grimdark version of the ghost.
That’s everything you need to know to run, fight, and hopefully not die to a pack of intellect devourers.
Until next time, folks, happy adventuring, and if you see a brain with legs, don’t try to pet it.
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I played my first tabletop RPG (Pathfinder 1e, specifically) in college. I rocked up late to the first session with an unread rulebook and a human bard called Nick Jugger. It was a rocky start but I had a blast and now, the better part of a decade later, I play, write, and write about tabletop RPGs (mostly 5e, but also PBtA, Forged in the Dark and OSR) games for a living, which is wild.