‘Why did it have to be mind flayers?’ See also here, here, and here. On the other hand, it was always nice to see one in Nethack; once you killed it, eating it would raise your Intelligence score a point. Of course, hopefully you had on a helmet that would keep it from eating your brain down to Intelligence 3 first.
Why, yes, that link does lead to a download that will likewise eat your brain through the wonders of text-based nostalgia. You want that to happen again? No? Then hit the tip jar for the travel fund, and maybe it won’t.
Moo hoo bwah hah.