I have decided to engage this somewhat controversial subject. Share my thoughts and explain them out.
So the controversy seems to be, are mind flayers on Athas? Do they fit thematically into Dark Sun, or do they clash with the setting? If they are in Athas, where do they come from? Are there better alternatives to the ithilids for my game?
I should note that I very much like canon and find it fun and challenging to play within those limits. If however, you decide to go outside those limits in your own game go for it. If you decide the mind flayers on Athas are refugees from a failed King Winnie Pooh in 100 Acre Wood revolt and like to smuggle marmalade sandwhiches under beer mug hats, donāt let me stop you.
Are Mind Flayers on Athas?
My personal answer is no.
This is heavily disputed. There is only one source anywhere that indicates they are. That is in the game Wake of the Ravager. Unlike its predecessor, it is regarded as questionable in terms of canon. In it, the mind flayers are infiltrating the Tyrian mines from below. They are seeking to harvest the miners for nefarious purposes. In terms of fitting into Athas, this both works and doesnāt. Most the things you learn about mines feel genuine and make sense. There are some boring machines which are totally out. Thereās a lot more you can do with mines, but I canāt sin on omission when dealing with a budget.
Where it falters, is the mind flayers themselves. There is nothing unique to them that distinguishes them from mind flayers of other worlds. They are doing the same shtick they would on any other world. You could easily transplant their underground city, the mind flayers and their antics into any other fantasy world and change nothing. They do not detract from Athas but neither do they add to it.
In essence, a missed opportunity.
Where do they come from?
Iāve seen a lot of theories that seriously over complicate this. You donāt need anything fancy or elaborate. No life shaping halflings, no Pristine Tower. The simplest explanation is that they were too far underground to be a part of Athasian. Not even Rajaat knew about them. Buried too deep and too alien.
If you really want them to be off worlders, I would recommend making their home base a crashed space ship or space station. Use setting and rules from Pathfinderās Numeria to present the players with something shockingly different.
If I donāt use mind flayers, then what?
If you stop and think about, Dark Sun comes with some excellent monsters that amply fill the shoes of mind flayers.
Mind flayers. What we are looking for are psionic, highly intelligent, scary, alien and organized.
Intellect Devourer- Though the Wake of the Ravager overlooks this, they are intelligent. Theyāll eat your brains, crawl in the skull and use your body like Guns and Roses uses a hotel room.
Psurlons- They exist in Athas. They meet all the requirements. Theyāll canon. Why not use them?
Chryzadue- Alien worm freaks. From Occult Bestiary. Fit it perfectly.
For me, the mind flayer controversy is a non issue. With so many, unique to Athas, I donāt see why you feel the need to use them.