Is taking down a mind flayer colony impossible in practice?

[NNescio]

Swap out immunity to nonmagical attacks with immunity to psychic abilities, and you've just solved the illithid problem, so I don't really think that changes the illithid vs. human colony math.

Illithids probably have thralls and other contingencies to deal with psy-immune enemies. It's still a useful tactic, but the party will still have to hang around to provide some supervision (and deal with those contingencies). There are much more resourceful than the typical human colony or city (unless said city is filled with high-level casters).

It's also harder to find something that is completely immune to illithids. Most constructs can still be rendered harmless with Levitate. Helmed Horrors are susceptible to psychic damage, and Flying Swords, while completely immune, are kinda lackluster in combat. They are nice to have around, but again the party would probably still need to stick around to supervise.

Regardless, I'd put that in the out-of-box strategies I'd expect to see in these scenarios. It is really the...



...hands-on scenario like this that I think the OP was talking about (given that he was worried about the illithids' dominates and mind blasts).

Illithids live underground and have a lot of early-warning detection defenses. This makes hands-off approaches much harder (other than, well, bribing a large enough Githyanki death squad).

Human colonies, on the other hand, are usually found on the surface and can be easily bombarded from a distance.

Edit:

Covered by Mind Blank, Int save proficiency (with Shapechange at least), and legendary resistances (unlike legendary active you do get these when Shapechanging), plus you don't have to end your turns in Mind Blast range because you fly 80' and have reach weapons.

What I'd be most worried about in this scenario is a thrall or mind flayer arcanist with Dispel Magic. There goes Shapechange, there goes Mind Blank, now you have to teleport away or it's Welcome To the Collective.

Send a True Poly'd Sim (or Shapechange for spell access, but concentration to maintain is riskier) then, along with True Poly'd Helmed Horror minions, plus the entire party behind an Astral Projection (with Mind Blank or Non-Detection)?

[darknite]

FYI - Mind Blank prevents psychic damage but will not keep you from being stunned by a Mind Blast.

[Damon_Tor]

AFAICT, nothing in the spell description precludes it.

It says they "plummet to the ground." Ergo, anything under the ground isn't likely to be effected.

[darknite]

It says they "plummet to the ground." Ergo, anything under the ground isn't likely to be effected.

Unless there's more ground under ground to plummet to?

[Willie the Duck]

<SNIP>

We can play contingency bingo until we are all sufficiently bored (and honestly this is already starting to sound like a Batman v. Superman debate where any point will be countered with 'Batman will be prepared for that'). Of course Illithid have thralls that need to be taken into account (and why the PCs will have gathered/summoned allies, which is why it is never really just 4 20th-level characters vs. anything). Likewise, cities probably have mages on top of the massed archers along the walls I was mostly thinking about. My only real point in using the human city is that I can readily see 4 20th-level characters each having an answer to dominate monster and mind blast, but still all but the guy shapechanged into a immune-to-normal-weapons monster still being able to be taken down by sufficient arrows. It was not a rigorous analysis and I'm unsurprised casual examination can find a bunch of weak points.

Here is my main point: I am guessing that the OP recently ran into multiple illithids at moderate level. My own group had a similar situation recently where we ran into 4-6 beholders when we were 11-12th level. It was indeed brutal. Being subjected to massively multiple save effects (yes many of them 'merely damage' but man does that not help when you get 60%+ of your hp taken out in one bad round). I can easily imagine someone thinking 'scale up the number appearing on this a few times and it's impossible. I don't care what level you are' I think that's a reasonable impression to get, but that in the end it is more hopeful for the high-level characters than this initial impression suggests. Particularly with illithids, because a whole lot of their abilities fall under the same category of with regards to what defenses work best against them. Also simply because of the difference between the mid-level play where 1-2 illithids/beholders are a reasonable opponent (and where 4-6 really sucks) and 20th level, where a lot of the strategy changes. Gate, Shapechange, legendary resistances, being able to get all or most of the party covered by Mind Blank -- these are things which can turn massively multiple dominate attempts and at-will area effect psychic damage from 'this is impossible' to 'well, we better not screw this up, but it is definitely doable.'

It says they "plummet to the ground." Ergo, anything under the ground isn't likely to be effected.

There is definitely a grey area about what 'ground' is, but the spell has no specified requirements about being outside or having a specific amount of ground (or 'ground') clearance in the way that spells like Call Lightning have.

[Ventruenox]

In my current game as a player, we are approaching the end of the campaign (3 sessions remaining). We have just learned that the Mind Flayers have infiltrated a large number of the populace, and have certainly dominated major NPCs that hold the political power.

I'm considering an unconventional approach to the problem: joining them. My character's main goal is peddling a pyramid scheme fake religion, with an emphasis that memories can be retained in your next life. Utilizing the Illithid collective may be able to do just that. I can propose that they continue their spread with the phony religion as a viable cover for their actions. I could also probably get some DM buy in to this if I utilize a cursed object I've had since the start of the campaign to disrupt the ceremorphosis, then go Hugh Borg on the collective.

It would be interesting, if nothing else, to be able to bypass the BBEG battle with a Persuasion roll. Mechanically, I know I can squeeze out somewhere between +12-20 with advantage on my roll. I doubt the other players' characters would be down with this, but I can see the players themselves finding it entertaining.

[nickl_2000]

It says they "plummet to the ground." Ergo, anything under the ground isn't likely to be effected.

Unless there's more ground under ground to plummet to?

The reason I asked was due to spells like Call Lightning (need to see the sky or have certain feet tall room) and my experience with level 9 spells is extremely low. There is nothing in it spelled out like that, so that was all I needed

[Brookshw]

Unless there's more ground under ground to plummet to?

Sounds like some strange line of effect rules.

Even if usable underground, range of sight seems to remain an issue.

[darknite]

Sounds like some strange line of effect rules.

Even if usable underground, range of sight seems to remain an issue.

There is absolutely nothing in the spell description that limits Meteor Swarm to an outdoor location. It works really well in an outdoor location because of Range = 1 mile and the ability to spread areas of effect. But nothing says it can't be used to some degree in a subterranean environment.

[Tharkun]

FYI - Mind Blank prevents psychic damage but will not keep you from being stunned by a Mind Blast.

You are correct but a wizard will have no trouble given max int and any saving throw boosts and the Paladin makes it pretty easy for the rest of the party given some prep.

[darknite]

You are correct but a wizard will have no trouble given max int and any saving throw boosts and the Paladin makes it pretty easy for the rest of the party given some prep.

Definitely a good strategy. Really depends on the extent of threat you're facing, the makeup of your party and the resources they have. I play plenty of high level games and illithids are still plenty scary, even in small numbers, especially when the best laid plans make contact with an enemy hivemind.

[Aprender]

Does anyone know the story of how Hercules cleaned the royal stables? He diverted a river rather than attempt the impossible task of cleaning the stalls individually.

Remember how much better your combat got when you started using the surrounding environment to improve your tactics? (I push him off the cliff!)

All of the above points are valid (and I love the Aliens references), but I want to throw out there that 20th level characters can and should be epic. They can affect gods and nature alike.

If there is a mind flayers base underground, flood it.... With lava.

Drop a mountain on the above ground citadel of mindflayers.

The Gith would gladly push the planet into the sun to rid the universe of a large Colony. Dial it back a notch, and you've got the start of a plan.

[Dork_Forge]

It really depends on the number of Illithids, number of thralls (and type), whether there is an Elder Brain and or a Ulitharid.

Realistically yes it's possible, by the time a party is 20th level they would have amassed a large amount treasure and allies to compliment their array of powers but it would be (and should be) very difficult. If the party doesn't have a Wizard or Paladin then it'll be harder, so it also depends on if the party are building for this.

If this was just theorycrafting then the answer is probably just yes, PCs have access to very powerful abilities and effects at 20th level, with the treasure and sway to bring to bear reinforcements. If you were considering running a game like this then just throw together a one shot, let the players know ahead of time that they'll be going after a colony to exterminate it and see how it goes, it'll be fun win or lose!

Sounds like a fun thing to try and a place where a GOO Warlock can really shine.

[Tharkun]

Definitely a good strategy. Really depends on the extent of threat you're facing, the makeup of your party and the resources they have. I play plenty of high level games and illithids are still plenty scary, even in small numbers, especially when the best laid plans make contact with an enemy hivemind.

Truth. I was in a level 1 party that saw an Illithid and I nearly died IRL. As a DM I would do quite a bit to make this hard. Multiple Mind Blasts are really brutal and there is so much crazy that is possible

[Damon_Tor]

Unless there's more ground under ground to plummet to?

There's a language problem here: ground has two different meanings.

Ground, noun
1. the solid surface of the earth; firm or dry land:
to fall to the ground.
2. earth or soil:
stony ground.

One is the definition I had used: it refers to the surface of the Earth (or, one presumes, any other planet). The other is the one you appear to be using.

This means RAW is unclear, which means we need to determine RAI. I think it's pretty clear the spell is intended to summon meteors (hence the name of the spell), which by definition fall from the sky. With that in mind we can infer that the designers intended the word "ground" in the sense of the first definition, not the second.

[dreast]

but the fact is that Int is usually a dump stat for non-Wizards and a DC 15, unless you have extraordinary and persistent cover, is not a chump save. If you're facing dozens of illithids, the law of averages is going to get you.

“Mind flayers suck.”

“Why?”

“They have powerful abilities that target a dump stat.”

“Why is it a dump stat?”

“Because only one class really uses it, and not much requires you to save with it. I wish they targeted Wisdom instead.”

“Well, maybe this has something to do with the fact that they are a legacy monster, and stat based saves weren’t really a thing. Perhaps we should look at what they did in AD&D 2e. Were they more fun to fight there?”

“Oh heck no! They could destroy people because they targeted a dump stat and if you ran out, it was instant death!”

“Why was it a dump stat?”

“Because only one class really used it, and not much else targeted it.”

“Well, at least they’re consistent. Maybe the answer should be that more creatures target Intelligence?”

“No way!”

“Why not?”

“Because then we couldn’t use it as a dump stat!”

[Protolisk]

There's a language problem here: ground has two different meanings.

Ground, noun
1. the solid surface of the earth; firm or dry land:
to fall to the ground.
2. earth or soil:
stony ground.

One is the definition I had used: it refers to the surface of the Earth (or, one presumes, any other planet). The other is the one you appear to be using.

This means RAW is unclear, which means we need to determine RAI. I think it's pretty clear the spell is intended to summon meteors (hence the name of the spell), which by definition fall from the sky. With that in mind we can infer that the designers intended the word "ground" in the sense of the first definition, not the second.

Meteor swarm just says blazing orbs of fire plummet to the ground. No explicit statement of coming from the sky, or not working indoors. Not even saying the actual size of those orbs, so they could be beads like Fireball, technically. Small beads falling 1 inch is still plummeting as long as it goes fast, as plummeting is just falling fast. Considering we can literally transpose matter and disrupt space, affecting how fast our newly summoned matter is going is hardly a challenge.

Either of your definitions can still mean earth as in dirt or rock, not explicitly a planet. Inviting that it needs to be "earth" the planet could mean that it won't work on Eberron or Toril, etc., but that is really nebulous and I won't go down that line of arguments.

You can deduce that the way it is written implies the spell must be from the sky, but if they really wanted that effect they would have done the same thing Call Lightning says, with specific heights and spell failure if there isn't enough space for a storm cloud. It doesn't, so it doesn't. Spells only do what they say they do and don't do what they say they don't do, so Meteor Swarm can summon blazing orbs that fall quickly, but not explicitly from the sky. Underground Meteor Swarm is viable.

Now, since underground areas tend to be tunnels and small caverns, and you need to see the points you are designating, good luck not catching yourself in the massive area of effect.

[MaxWilson]

Now, since underground areas tend to be tunnels and small caverns, and you need to see the points you are designating, good luck not catching yourself in the massive area of effect.

Hmmm, I wonder if Contingency: Dimension Door could help you out there.

"When: blazing orbs of fire fall from the sky or I am reduced to less than 30 HP, Then: Dimension Door me 500' straight up (and I'll Feather Fall down)."

Does the fire from a Meteor Swarm expand faster than a Contingent spell can trigger? Inquiring minds want to know, probably through experimentation.

[Zuras]

Come on people, you’re not even trying. A 13th level Cleric can use Conjure Celestial to get a Couatl, which is conveniently immune to non-magical weapons and psychic damage.

[MaxWilson]

Come on people, you’re not even trying. A 13th level Cleric can use Conjure Celestial to get a Couatl, which is conveniently immune to non-magical weapons and psychic damage.

But not, however, to Dispel Magic. It's still a conjured creature.

Nor is it immune to Plane Shift, or being stunned by a Mind Flayer's tentacle attack, or Dominate Monster.

[Lunali]

This, right here. That's why the party accumulated all of that treasure ... to offer the Gith a bit of coin for the raid.

That's just bad treasure management, you don't pay the gith to raid mind flayers, you charge them for it.

[MaxWilson]

That's just bad treasure management, you don't pay the gith to raid mind flayers, you charge them for it.

Well-played!

[sithlordnergal]

Honestly? No, it isn't. You would need to be a higher level, but I could see a group of level 12 to 13 PCs surviving a mind flayer colony. As for extinguishing it, a level 20 party that is reasonably optimized should be able to do it with ease. Just off the top of my head, a party with a Wizard, Rogue, Cleric, and Paladin with max charisma should be able to handle it.

[Protolisk]

Come on people, you’re not even trying. A 13th level Cleric can use Conjure Celestial to get a Couatl, which is conveniently immune to non-magical weapons and psychic damage.

This is a great option too. All the initial question asked was if max level characters could do it. I think the general view is "yes, they can". Moving the goalpost to "how low a level can you go" is not what was asked, but it is definitely fun to think about. Then again, most answers are about level 9 spells, so full casters by level 17 could manage it.

A level 10 Great Old One warlock would have resistance to psychic damage, but also reflects that damage back on the attacker. No illithid is actually resistant or immune to psychic damage, so with enough healing a GOOlock could figure something out. The stunning effects of Mind Blast would still need to be contended with...

Mind blast itself is a "magical" effect. So gnomes could get advantage against Mind Blast from level 1, as well as the Dominate spells. Helps that all gnomes get +2 to Int off the bat to help with saves against Mind Blast. Get yourself some level 10 gnome GOOlocks and head on down to Mind Flayer town. They are still warlocks, so darkness could be abused against the mind flayers that have mind blast on cooldown, since Mind Flayers can't perceive the gnomes. An Elderbrain could, though, but a Mind Blast needs to be successful for their funky abilities to work well. Need to get within 60 feet of the gnome squad to stun-incapacitate them. Too bad the actual spells in most Mind Flayer's repertoire requires sight, because again, Magical Darkness. A squad of Gnomes could stagger their Darkness casts so that they aren't completely incapped by an errant mind blast.

If gnomes abuse Eldritch Blast and the pushing abilities from invocations, they could keep them at bay. And with Devil's Sight, the gnomes and mind flayers should see each other at the same distance, but the gnomes have magical darkness on their side so it's kind of moot anyway. Just hope that your combats take place in at least 90 foot areas so you have enough space to knock the flayers back, lest they walk 30 feet forward and then catch you in a 60 foot cone.

If level 10s could cheese this, higher levels should be able to as well. Of course, the flayers' minions might screw with these tactics, as well as plain old un/luckiness, but this is a workable plan. It's not absolute cheese like Couatl summoning, but it can hold its own.

[MaxWilson]

This is a great option too. All the initial question asked was if max level characters could do it. I think the general view is "yes, they can". Moving the goalpost to "how low a level can you go" is not what was asked, but it is definitely fun to think about. Then again, most answers are about level 9 spells, so full casters by level 17 could manage it.

A level 10 Great Old One warlock would have resistance to psychic damage, but also reflects that damage back on the attacker. No illithid is actually resistant or immune to psychic damage, so with enough healing a GOOlock could figure something out. The stunning effects of Mind Blast would still need to be contended with...

Mind blast itself is a "magical" effect. So gnomes could get advantage against Mind Blast from level 1, as well as the Dominate spells. Helps that all gnomes get +2 to Int off the bat to help with saves against Mind Blast. Get yourself some level 10 gnome GOOlocks and head on down to Mind Flayer town. They are still warlocks, so darkness could be abused against the mind flayers that have mind blast on cooldown, since Mind Flayers can't perceive the gnomes. An Elderbrain could, though, but a Mind Blast needs to be successful for their funky abilities to work well. Need to get within 60 feet of the gnome squad to stun-incapacitate them. Too bad the actual spells in most Mind Flayer's repertoire requires sight, because again, Magical Darkness. A squad of Gnomes could stagger their Darkness casts so that they aren't completely incapped by an errant mind blast.

If gnomes abuse Eldritch Blast and the pushing abilities from invocations, they could keep them at bay. And with Devil's Sight, the gnomes and mind flayers should see each other at the same distance, but the gnomes have magical darkness on their side so it's kind of moot anyway. Just hope that your combats take place in at least 90 foot areas so you have enough space to knock the flayers back, lest they walk 30 feet forward and then catch you in a 60 foot cone.

If level 10s could cheese this, higher levels should be able to as well. Of course, the flayers' minions might screw with these tactics, as well as plain old un/luckiness, but this is a workable plan. It's not absolute cheese like Couatl summoning, but it can hold its own.

How many Mind Flayers are you envisioning in this "how low can you go" challenge? (Agonizing Repelling) Eldritch Blast won't keep more than a handful of mind flayers at bay, for instance. Won't work on even as many as a dozen mind flayers.

In theory you could wipe out the whole colony with a level 8 Orcish Rogue 2/Shadow Monk 6, as long as you've rolled a 3 on Int. After Orc penalties, your Int is too low for Intellect Devourers and Elder Brains to detect your presence, so you can abuse the Cunning Action (Hide) + Skulker + Pass Without Trace combo to surprise and then basically pick off Mind Flayers and/or thralls whenever they're isolated from the main body, using your surprise round/martial arts/stunning strike. Every two hours you withdraw and take a short rest to regain ki, then do it again. You're basically Pennywise the Dancing Clown terrorizing the illithid Derry. Might take you several weeks to completely depopulate the colony but you've got plenty of time.

From a RP angle, though, it's very implausible that an Int 1 Orc would ever actually invent such tactics, or be motivated to wipe out a mind flayer colony in the first place.

[Protolisk]

How many Mind Flayers are you envisioning in this "how low can you go" challenge? (Agonizing Repelling) Eldritch Blast won't keep more than a handful of mind flayers at bay, for instance. Won't work on even as many as a dozen mind flayers.

In theory you could wipe out the whole colony with a level 8 Orcish Rogue 2/Shadow Monk 6, as long as you've rolled a 3 on Int. After Orc penalties, your Int is too low for Intellect Devourers and Elder Brains to detect your presence, so you can abuse the Cunning Action (Hide) + Skulker + Pass Without Trace combo to surprise and then basically pick off Mind Flayers and/or thralls whenever they're isolated from the main body, using your surprise round/martial arts/stunning strike. Every two hours you withdraw and take a short rest to regain ki, then do it again. You're basically Pennywise the Dancing Clown terrorizing the illithid Derry. Might take you several weeks to completely depopulate the colony but you've got plenty of time.

From a RP angle, though, it's very implausible that an Int 1 Orc would ever actually invent such tactics, or be motivated to wipe out a mind flayer colony in the first place.

I was mostly thinking tunnels. If they kept to tunnels that are only wide enough for a few at a time 4 gnomes can do 8 attacks at advantage and knock the flayers back a lot. Works for 2-3 or so flayers at a time. Level 11 gets up to 12 attacks per turn. Too open of areas does make it worse. You idea of working around 1 int is pretty hilarious, not gonna lie.

[MaxWilson]

I was mostly thinking tunnels. If they kept to tunnels that are only wide enough for a few at a time 4 gnomes can do 8 attacks at advantage and knock the flayers back a lot. Works for 2-3 or so flayers at a time. Level 11 gets up to 12 attacks per turn. Too open of areas does make it worse. You idea of working around 1 int is pretty hilarious, not gonna lie.

Don't the mind flayers just back off around a corner until your Darkness spell slots run out?

[Protolisk]

Don't the mind flayers just back off around a corner until your Darkness spell slots run out?

Then you just approach the corner and then start blasting them again. They still can't see you, so attacking blind is useless. And full cover blocks Mind blast as it doesn't ignore cover like Fireball does. So a single gnome might get hit, but not all of them. Continue blasting and hoping to knock them back further still, but yeah it breaks down. But again, resistant to psychic and advantage against the saves.

Like I said it's not perfect, but it is workable. If level 10s have a reasonable plan, then max levels should be able to do it no sweat.

[JackPhoenix]

Taking out the Elder Brain is crucial, as it is the centerpiece of any mind flayer colony. It also screws up mind flayer warning system.


Funnily enough, Elder Brain needs to breathe, and lacks amphibious trait. You can use that in multiple ways, burying it in rock with Earthquake or Transmute Rock, or even drowning it. It can Plane Shift, but only once per day, PS is inaccurate, and the brain can't survive long outside its brine pool.


Steel Predator is immune to psychic damage and stunned and charmed conditions. Also to non-magical physical attacks of any minions mind flayers may have. It's too big to be grappled by mind flayer tentacles. While it's Int of 4 is too high to be invisible to Elder Brain, it'll propably get ignored for at least a while, and you can always slap Nondetection on it. And you can buy (or rather hire) those things in Sigil.

Get a sample from the brine pool to mark the Elder Brain as target, and release the hounds.


Another alternative is True Polymorphing someone into a demilich. Same crucial immunities as Steel Predator. It also has Legendary Resistance in case the mind flayers try some other trick. Then there's the fun part: Howl has 65% (It's not magical so no advantage due to magic resistance of dropping any mindflayer in 30' radius to 0 hp. It's neither spell nor attack, so it doesn't break invisibility. Imagine invisible screaming skull flying through the colony, killing everything around itself. Too bad it's undead, so you can't use Shapechange instead of True Polymorph to retain your class abilities.

[MaxWilson]

Then you just approach the corner and then start blasting them again. They still can't see you, so attacking blind is useless.

When you turn the corner, you get hit with a bunch of readied Mind Blasts from prone Mind Flayers. All you've done is chase them until the terrain favors them more than you. This plan seems like a recipe for suicide even if the mind flayers DON'T do anything tricky like envelope you or mousetrap you.