I've looked around wikis and question boards all over, but, as of the moment, I can't even find anything regarding an interaction of any kind between a displacer beast or similar creatures and Illithids. I could just do as I plan to and simply homebrew it, but with nothing even mildly similar, I don't have much to go off, and I don't necessarily want to just slap face tentacles on a displacer beast.

If anyone is curious about the context: I am making a Mindflayer colony encounter for a campaign I DM, and as a result of me being a madman, it has become what one would call "unique" e.g. It's a portion of an expanding breed of arcanist Illithids, and this particular one has taken to experimenting on creatures Illithids normally wouldn't in attempts to optimize their colony as a whole.

Post answer edit: I am including this link to a Google Doc containing a 5e stat-block I have made for the Lugrithion along with basic descriptive info if anyone seeing this has an interest in it.

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    \$\begingroup\$ "They've taken to experimentation" is all the excuse you need. Even if canonically it doesn't work, that's only because canon never met these guys. \$\endgroup\$ Jun 19, 2023 at 20:20

2 Answers 2


A displacer beast can't undergo true ceremorphosis

As indicated in sources from 2e's The Illithiad to 5e's Volo's Guide to Monsters, ceremorphosis only works on humanoids, and then only on select kinds. A displacer beast implanted with a tadpole could become some sort of aberrant monstrosity, but not a true mind flayer, and would not be accepted as an equal in society as a result, any more than similar creatures such as the mindwitness (an implanted beholder) or urophion (an implanted roper).

...but it can become something pretty awful

The 3rd Edition Fiend Folio offers us a half-illithid template to reference, which has some solid basics as well as the aforementioned face tentacles. Easy way to go, really, but if you want to play with the concept a bit more, here are a few suggestions:

Dragon 281 offers a table of sample illithid names. From this you might want to call your monstrosity a lugrithion (roughly "feared darkness"), maanzehoon (roughly "the one outside law"), or xallibosk (roughly "master of pain") if you'd like to match the general cadence and "ring" of illithid critters. I'll be using lugrithion in the below.

• Rather than the implantation transforming the face to be capable of cranial ingestion, it should transform the displacer beast's own tentacles; perhaps it grows a second pair, and each one's pads become lampreylike mouths that can be used to pin down a potential victim for extraction. I'd suggest maintaining a hold with two of these might be enough, since they're larger surfaces; this immediately makes the lugrithion a much more melee-cadenced foe, as they know they are considerably more deadly and have the spare tentacles to threaten a second foe at the same time. In exchange for this increased melee deadliness, I would not carry over the mind flayer's stunning effect on its tentacles.

• Adjust the spell-like abilities; remove dominate monster and replace with something fear-based as a way to emphasize the calculating predation of the lugrithion - this is a combination of the cold and unfeeling mind of an illithid with the malice and catlike attitude of the displacer beast. You could also choose instead to emphasize its illusory capabilities.

• Retain the magic resistance, telepathy, and mind blast.

• Physically, the creature would retain the dark coloration of the displacer beast but would be hairless and slightly slimy, with a foul sheen glistening from it. Its eyes would be glowing white and in place of its muzzle would be moist smooth flesh that throbs and flutters as the lugrithion breathes, since it has no need to vocalize and its food is ingested through its tentacles. Its digits might also be a bit more elongated and webbed, spreading in a manner disturbingly reminiscent of a clammy human hand.

• In short, a large bestial thing that's a mix of a panther, a Xenomorph, and Gollum, with lashing tentacles on its shoulders that can be used to extract brains.

• The attitude of the lugrithion, as noted above, would combine the cold disconnectedness of illithids with the sadistic impulses of the displacer beast, producing a nasty, extremely intelligent predator that uses stealth, confusion, fear, and disruption long in advance of making a direct attack, purely to "season" the brains of its prey with fear. It would bear no true loyalty to any other being and would remain in the community out of either fear or convenience. Between telepathic whispers, manipulation via illusions or fear effects, and the awesome power of a mind blast, a lugrithion should be an exercise in anticipation and dread.

Why don't flayers make more of these elsewhere? Well, perhaps they do, but how wise is it to upgrade a powerful apex predator to make it more psionically adept and physically vicious while also leaving it with absolutely zero loyalty to you? Enough lugrithions have likely made the calculated decision to snack on their own creators that they remain an uncommon encounter even for dedicated delvers of the Underdark - and thus a perfect surprise for unwary adventurers.

Hope this helps!

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    \$\begingroup\$ +1 for the additional context from the game's history. It sounds like someone got pretty exited by the idea of a mind-flayer displacer beast crossbreed here :) \$\endgroup\$ Jun 17, 2023 at 5:49
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    \$\begingroup\$ Oh aye, I'll stat it for 3.5 soon enough now that the idea has been incepted. \$\endgroup\$
    – afroakuma
    Jun 17, 2023 at 5:59
  • \$\begingroup\$ Yes! Exactly what I was looking for in every sense of it, between the naming (which I do like Lugrithion the most) and the kind of twisted ceremorph transformation that lines it into the same category as the other, not actually a mindflayer illithid-kin+, while still making it unique and interesting. And as someone who's a sucker for this kind of stuff, I also very much appreciate that you referenced/cited specific sources. \$\endgroup\$ Jun 17, 2023 at 18:22

In 5e, only humanoids undergo ceremorphosis

Ceremorphosis is described in Volo's Guide to Monsters, p. 72:


Mind flayers don't reproduce in the traditional sense. Instead, they lay eggs from which hatch tadpole-like creatures that are used to make more of their kind through a process called ceremorphosis. First, a captured humanoid is rendered docile by a blast of psionic power. A newly hatched tadpole is inserted into the victim's cranium, usually through a nostril or ear canal. The tadpole grows as it devours the humanoid's brain, attaching to the victim's brain stem and becoming its new brain. Over the course of a week, the humanoid body changes form, and a new mind flayer comes into being.

So rules as written, only humanoid creatures can undergo ceremorphosis, and since displacer beasts are monstrosities, they do not.

That of course should not prevent you from home-brewing something like this, if you set your mind to it. After all, the rules are more like guidelines, and explicitly put the DM in charge (DMG, p. 4):

The D&D rules help you and the other players have a good time, but the rules aren't in charge. You're the DM, and you are in charge of the game.


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