By Alan McCoy from Dungeons & Dragons: Fundamentals
How to build challenging encounters against
Mind Flayers (aka Illithids)
Also known as Illithids in Advanced Dungeons and Dragons second edition.
Note: This has been prepared utilizing only the Fifth Edition Core Rules. The Mind Flayer can be found in the Monster Manual (page 221 – 222).
For convenience, and to avoid confusion, I will be using the term Illithid as the race name wherever possible.
While there are general similarities between the appearance of the humanoid races – Tall, slender beings with legs, arms and a head.
Even if they tend to wear clothing, few would mistake an Illithid for any form of humanoid – the differences far outweigh the similarities.
The sickly purple-grey pallor of their skin.
The three fingered hand and the four tentacle-like protuberances that snake from their heads – as if is some primitive octopi was consuming them headfirst – are a sight that once seen will never be forgotten.
The origin of the Illithid has either never been known, or is now long forgotten.
What is known is that the Illithids are not a native species to any known worlds.
This species is utterly alien, and are travelers from other dimensions and unknown world.
Ultimately, their world of origin is unimportant!
They have spread far and wide, and are now the scourge of sentient species everywhere!
These creatures have mental powers that seem to fall outside the scope of the worlds they visit, being neither arcane, divine or physical – using these abilities has allowed them to dominate and enslave species after species.
Illithid are insidious masterminds that have enslaved and harvested unknown numbers of races.
It is possible that their harvest has eliminated some of them.
Races known to have been previously enslaved by the Illithid include: The Duergar. The Gith. The Grimlock and the Kuo-Toa.
Each of these races claims to have risen and thrown off the yoke of Illithid slavery.
While the Illithid claim that they released these races once their minds had grown too bland, stating that the flavor would be improved by a few eons of cultivation in the wild.
They will be reclaimed, eventually…
While it is true that the former slave races of the Illithids are free as a race, there are members of these races still under Illithid control.
It is likely that these mind-controlled slaves will be encountered with their former master race.
Additionally, there have been reported incidents where the Illithid have used Ogres, Quaggoths and Troglodytes minions.
In short, encountering the Illithid is quite likely to be an encounter with a polyglot of controlled creatures – this could include an Intellect Devourer, which is either a guardian, an experiment or a pet.
It is rare, but not unheard of, to encounter a singular Illithid!
Those Illithid that have chosen to separate themselves for a time, always do so for a purpose.
Every enclave, settlement or city of the Illithid has a Hive Mind.
While this is sometimes a simple strengthened rapport between the individuals of the enclave, this can also indicate the presence of an Elder Brain.
An Elder Brain is a massive being that, to most humanoids, looks like a massive brain floating in a briny solution.
The Elder Brain can communicate with all the members of the enclave at once, and will attempt to coordinate their activities for both maximum efficiency and security.
Every Illithid innate power of levitation makes the use of stairs or ramps unnecessary.
Thus an enclave will be multi-level and difficult to navigate for those who lack some means of traversing the three-dimensional nature of the architecture.
So, why conquer and enslave?
What do these beings want?
Quite simply, to an Illithid, sentient minds are food.
They subsist on the brains of humanoids!
The enzymes, hormones and material provide the sustenance.
While the psychic energy, the memories, thoughts, experiences and personality, provide the unique flavor.
If the race has any major weakness, it is this!
They are not satisfied with bland meals that merely provide sustenance, they want meals that are worth eating.
It is this drive that has caused them to release – or allow to escape? – previously harvested races.
To make them once again food “fit for the table”!
When not engaged tending their herds of sentients, the Illithid consider themselves quite sophisticated.
They collect art, and study the sciences of the worlds in which they live.
They collect and study magical lore captured from subjugated individuals and races.
There is a rumor of Illithid that have learned to supplement their powerful mental energies with magic.
If true, these Illithid Arcanists would be exceptionally dangerous.
Illithid reside in the Underdark, and are usually met there.
They have been known to contact, and even ally themselves, with other Underdark communities when it suits them.
Such alliances are always temporary at best, though the other parties might think them long term.
Additionally, Illithid have been encountered when they have plane shifted to another plane of existence.
They have been known to visit slave auctions of the fabled City of Brass, on the Elemental Plane of Fire.
The Efreeti are considered a valuable source for special slaves and rare meals.
Their Written Language is known as Qualith – essentially a tactile written language that can be read by an Illithid’s tentacles.
For translation purposes, these writings are always in a four-line stanza.
Step 1) Determine the probable Strategy
The primary fighting philosophy of the Illithids is one of evaluation.
It has minions that will fight for it and will, if necessary, send those minions charging to their death in order to provide it with time to escape.
Usually the goal is to capture and subdue a potential enemy and then enthrall it, or consume it.
The “Hive Brain” of the Illithids provides instant communication between members of the same Enclave within five miles or so.
If an elder brain exists, the communication range is far longer, and can be used to relay information to other members of the hive.
Illithids are all too aware of their limited physical abilities.
They know that in any purely physical confrontation they would be vulnerable, and probably defeated.
Secrecy and stealth are part of their overall defense plan for the Enclave.
It is not unknown for them to utilize their plane shift ability and hunt far away from their actual home.
If it is necessary for an Illithid to sacrifice themselves and suicide in order to avoid leading others to the hive, this is a step that they are willing to take.
Step 2) Determine Tactics
Essentially, the fighting tactics of the typical Illithid is to utilize their minions and slaves to fight their battles for them.
They will utilize their levitation ability and available magic items to stay away from direct physical battle.
Should a likely target present itself, someone that they read as having a weak will with their Detect Thoughts ability, an Illithid will take the opportunity to use Dominate Monster, and add a party member to its minions.
Where necessary they will utilize their Mind Blast from a distance to allow them to damage and stun those in combat with their minions, who, already being under control of the Illithid, are largely unaffected.
Because this ability must recharge, Illithids always do their best to utilize it to maximum effect.
Once its minions have subdued a victim, or the mind blast has stunned one, the Illithid will make Tentacle attacks to further subdue the target.
The Stunned condition provides Advantage to hit on these attacks.
If the Illithid has chosen to consume the victim, they will approach the incapacitated and stunned prey, and utilize their tentacles to perform their Extract Brain ability.
This 10d10 damage attack will instantly kill any creature brought to zero HP or less.
Step 3) DM Tips and Observations
Technically, the Illithid lacks the actual capability of making more than very temporary minions.
The spell Dominate Monster is a one-hour concentration spell, even the weakest of minds is highly likely to break free long before then.
As Dungeon Masters, we need to hand wave and declare that a behind the scenes ability is taking place behind the scenes.
As I personally hate to leave any such ability completely undefined, I will suggest utilizing the Enslave ability of the Aboleth as a model (see the Monster Manual page 13-14).
You could limit the ability by making this something only a Hive Mind or an Elder Brain could do.