Squid-Faced Brain Munchers
The Illithids are called “mind flayers” by the people of the surface, “mind rulers” by the rightfully fearful denizens of the underdark, and “squidly diddlys” by me, because I think it’s funny. Illithids have been murdering adventurers for their sweet juicy brains since the 1st edition of D&D, and they’re in the running as one of the most iconic and uniquely D&D monsters out there. So, how do you best keep your brains unmunched? How should you run them in your adventures? Put on a very thick helmet as we delve into the underdark and go through everything you need to know.
Mind Flayer Fundamentals
Illithids are alien beings… Literally, in most implementations of their lore they actually arrive from another planet or another plane. They’re meant to feel alien as well, these aren’t just some snarling monsters, they’re highly intelligent psychic beings from an utterly alien world that is nearly impossible for us to understand. One aspect of their culture that is easy to understand is that they do not mean us well.
The whole brain eating thing is fundamental to their culture, and it’s not a choice, they will literally wither away and die if they don’t consume the brain matter of an intelligent creature at least every few months. This understandably makes diplomacy with them difficult, and even when “deals” are struck, they’ll still think of everything not-illithid as a potential meal. Mind flayers think of themselves as masterminds, plotting and manipulating everyone around them to serve their own needs.
Mind Flayer Physiology and Culture
Adult illithids are hairless humanoids that stand about 6 feet tall, with 4 long tentacles dangling down from their mouths. They’re naturally powerful psions, and when fed a steady diet of humanoid brains they tend to exude a slick protective mucous coating. A lot of how they function physically and how their culture functions has to do with their life cycle, so bear with me.
Mind flayers are sexless, but once or twice in their lifespan they’ll lay a clutch of eggs which then hatch into tiny illithid tadpoles. These little squids get dumped into the elder brain tank (again bear with me) where they hone their psionic instincts and fight each other for dominance, cannibalizing the weaker ones and often getting consumed by the elder brain itself.
The tadpoles that survive this process basically “earn the right to live”, but we’re not done with the weirdness. The chosen “worthy” tadpoles then must be shoved into a living humanoid’s skull, where the little baby mind flayer parasitically consumes the host’s brain matter, and essentially becomes the new brain. With the baby illithid parasitically “piloting” the humanoid creature, the body slowly grows into a fully-fledged adult illithid. This is where we get all the whacky “mind flayer dragons” and “mind flayer ropers” from. What we think of as a “standard mind flayer” is the result of injecting an illithid tadpole into most humanoids, putting the tadpole in more unusual creatures can create some unusual mind flayers.
But what about that elder brain thing I mentioned? You can think of the elder brains functionally as the “queen bees” of the illithid world. An elder brain is a literal giant brain with a ton of tentacles floating around in goo, and they’re extremely powerful psions. Illithids like their independence, but they’re cowards at heart, and typically band together into colonies centered around an elder brain. The elder brain has complete control over its mind flayer subjects, and it’s better to think of each colony as a single super-organism, rather than a group of individuals. Each mind flayer may vie for position against each other, but they’re utterly powerless against the elder brain’s psychic commands.
The elder brain feeds off many of their tadpole young, and the brains of dead mind flayers, each new brain adds to the elder’s overall intellect and the colony grows smarter with every bite. Which finally brings us to how the brains get there in the first place. Very rarely, a tadpole is born as an ulitharid. These guys have a couple extra face tentacles and are even smarter than the average mind flayer. The other illithids will treat it as a minor godly being, as it’s basically an elder brain larva. For the sake of the species, the elder brain will begrudgingly accept this new rival, who will take some illithid followers to form a new colony elsewhere. Eventually once they’ve settled, the ulitharid will consume a ton of brain matter and transform into a new elder brain.
But how does a mind flayer society actually work? On the backs of slaves mostly. Their fearsome psionic powers are enough to subdue a lot of various humanoids. The more useful ones are kept as psychically dominated slaves, the rest are brain snacks. Of course, in times of trouble even the most useful servant can double as a brain ration. Slaves run the city, ruled by the mind flayers, who are in turn subject to the absolute psionic power of the elder brain.
It is only when mind flayers are sent away to gather intelligence or carry out the elder brain’s orders that they have a chance at independence again. These “renegade mind flayers” sometimes try to form colonies of their own, or even ally themselves with other humanoids, but any independent thought or personality melts away if they’re brought within the psychic grasp of an elder brain.
Finally, all this usually happens in the dark, quite specifically the underdark. Mind flayers live on this world of the material plane to hide away from interstellar threats and the sunlight. They’re physically hurt by the sun, and the dark caverns beneath the surface world are perfect for them. Most mind flayer colonies exist in the underdark or are hidden away on other planes.
Mind Flayer Stats
There are a ton of mind flayer variants from back in 3rd edition, from illithid dragons to the mighty elder brains themselves. Now in 5th edition we’ve got the standard version, a couple of mind flayers with some extra spells, and a full-fledged mind flayer lich. We also got the gnome cenomorph variants out of Icewind Dale. For the moment, let’s focus on the standard version, in all its squidly goodness.
Medium aberration, lawful evil
Armor Class 15 (breastplate)
Hit Points 71 (13d8 + 13)
Speed 30 ft.
STR DEX CON INT WIS CHA
11 (+0) 12 (+1) 12 (+1) 19 (+4)17 (+3)17 (+3)
Saving Throws Int +7, Wis +7, Cha +6
Skills Arcana +7, Deception +6, Insight +6, Perception +6, Persuasion +6, Stealth +4
Senses darkvision 120 ft., passive Perception 16
Languages Deep Speech, Telepathy 120 ft., Undercommon
Challenge 7 (2,900 XP)
Magic Resistance. The mind flayer has advantage on saving throws against spells and other magical effects.
Innate Spellcasting (Psionics). The mind flayer’s innate spellcasting ability is Intelligence (spell save DC 15). It can innately cast the following spells, requiring no components:
At will: detect thoughts, levitate
1/day each: dominate monster, plane shift (self only)
Tentacles. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) psychic damage. If the target is Medium or smaller, it is grappled (escape DC 15) and must succeed on a DC 15 Intelligence saving throw or be stunned until this grapple ends.
Extract Brain. Melee Weapon Attack: +9 to hit, reach 5 ft., one incapacitated humanoid grappled by the mind flayer. Hit: The target takes 55 (10d10) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.
Mind Blast (Recharge 5-6). The mind flayer magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Using a Mind Flayer as a DM
A renegade (single) mind flayer can be an excellent BBEG (big bad evil guy) for tier 1 adventures, or an entire colony can be a major threat for even tier 3 or 4 adventurers. However, they’re really meant to be a cerebral opponent and I don’t recommend just throwing them at the party.
Mind flayers are schemers and manipulators. Set one up as the “mysterious benefactor” buying up the slaves from all the local raiders. Or have the players investigate a shadowy cult whose members keep disappearing only to discover the horribly squiddy truth. Mind flayers shouldn’t jump out at players and attack them, they should be the masterminds behind it all. Give them a swivel chair to spin dramatically as they give a villain monologue and stroke a pet intellect devourer.
In terms of actual combat, mind flayers don’t have a ton of hit points or a terribly high AC, though magic resistance stops them from being outright squishy. Their threat is in the combination of their mind blast and extract brain abilities. The mind blast is a powerful cone of psychic damage with a stun attached, and stunned players are ripe for the brain eating. If the mind flayer gets a hold of a stunned or grappled PC and holds onto them all the way to their next turn, that PC is almost certainly dead. Not down, dead, brain eaten. The risk of straight up killing a PC with a mind flayer is quite high, so use with caution.
Especially since mind flayers are rarely caught on their own. Even a renegade mind flayer will likely have a bunch of enslaved servants to defend themselves with. Intellect devourers are excellent and flavorful choices for this, and most drow stat blocks you come across will make great illithid servants for your encounters. Just try not to overdo it if you want to avoid a TPK.
Fighting a Mind Flayer
Mind Flayers are extremely dangerous, but they can also be glass cannons. They have comparatively low hit points and AC, but a potentially deadly damage output. They have magic resistance, so pushing through the damage spells is unlikely. But if you manage to sneak up with a bunch of martial characters an ambush can easily kill an unaware illithid outright.
As a BBEG, your party isn’t likely to get that opportunity though. In a “fair fight” you’ll have your work cut out for you. The big threat is the mind flayer’s extract brain ability. Chances are, if it gets this ability off, one of your party members is straight up dead. To use this ability, the mind flayer must start their turn grappling a creature, so do everything in your power to make sure that doesn’t happen. Counter grapple, use spells like thunderwave to push it back, do everything and anything to get out of its clutches. The mind flayer will attempt to stun everybody with its mind blast and will likely try to dominate somebody into becoming a brain snack. In both cases though, it’s still going to take a turn for it to grab a hold of somebody.
The mind flayer’s damage output without snacking on brains is manageable and given its low hit points it should go down in only a couple rounds, unless it has a lot of adds backing it up. If you focus damage it down and keep everybody out of its grapple, you should be fine.
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Last updated: January 27, 2019
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