If you need Mind Flayers with an extra dose of creepiness, use the Phrenic Scourge. I run Spelljammer with these substituted for Mind Flayers and it makes a big difference.
For one, you cannot read their mind because it's not one mind but many. You aren't going to win a psionic battle with these space slugs because you are vastly outnumbered already.
They are straight-up alien. No two will be exactly alike. They leave madness in their wake.
As a GM, I feel the inner Bwa Ha Ha every time I include one of these. Go and do likewise. 🙂
15. COPYRIGHT NOTICE
Open Game License v 1.0, Copyright 2000, Wizards of the Coast, Inc.
System Reference Document Copyright 2000-2003, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook, Skip Williams, Rich Baker, Andy Collins, David Noonan, Rich Redman, Bruce R. Cordell, based on original material by E. Gary Gygax and Dave Arneson.
Unearthed Arcana Copyright 2004, Wizards of the Coast, Inc.; Authors Andy Collins, Jesse Decker, David Noonan, Rich Redman
The Iconic Bestiary: Classics of Fantasy Copyright 2005, Lions Den Press; Author Ari Marmell
The Grand OGL Wiki, http://grandwiki.wikidot.com Copyright 2008-2011 Purple Duck Games; Authors: Mark Gedak, Alex Schroeder, Joel Arellano, George Fields, Yair Rezek, Mike Whalen, Shane O'Connor, Mike Rickard, John Whamond, Bill Browne, Eric Williamson, Slatz Grubnik, Charles R. Wenzler Jr, John Fraser, Jonathon Thompson, Thomas Boxall.
These guys make a perfect foil to Mind Flayers. Best of all, they are OGL!