There were a few source books released by Wizards of the Coast and others that expanded on the background of Illithid, and there were two things I found really interesting:
- One book went way into Mindflayer communities, and how they have this motherbrain thing and a spawning pool and lamprey-like young and ugh it is squeegly!
- One possible background for the species is a multiverse-spanning empire of humans from the far far far future, after they’ve mutated due to dealings with the Outside or whatevs, and then something sent them, or causes them to flee, back through time.
Illithid are brand IP I think, so I am uninterested in their exact implementation. Even with the serial numbers filed off, I find the concept kinda strange in that “this is D&D!” way. However! I like the two ideas I outlines as separate concepts, or perhaps even opposing forces: humans in the far future have to find psychic lampreys from the Far Realm that ultimate turn into motherbrains capable of piercing the dimensions where time don’t exist, so the only way for the humans to survive is to timeleap and prepare the multiverse for the way to come, possibly by means of a super-soldier project in the astral plane (looking at you, Gith!).
I will have to track it down, but my favorite comic involving a mindflayer is from Dragon magazine, and involves mindreading. 