A brief guide to mind flayer substitutes

So Mind Flayers are considered product identity by Wizards of the Coast and third-party publishers cannot mention them. Months ago I posted a brief post about how my setting would replace them with several races that worship the big Cthulhu himself, but in this post I would like to discuss substitutes in an out-of-character fashion.

Substitutes have appeared in a variety of supplements by third-party publishers, but nothing has really taken off it seems to me. Most were one-offs that were never again supported by publishers, although a few received a surprisingly detailed depiction. The ones that stood out to me were:

• Encephalon gorger. Originally appeared in the Tome of Horrors series by Necromancer Games/Frog God Games. They loosely resembled vampires but harvested cranial fluid to power their technology. They still appear in adventures by that publisher and were reprinted/converted in their Fifth Edition Foes.
• Phrenic scourge. Originally appeared in The Iconic Bestiary series by Lion's Den Press/Purple Duck Games. They appeared as psychic masses of tentacles that reproduced by implanting their ravenous larvae inside of living hosts. They were greatly expanded on by Dreamscarred Press in their 3.x/PFRPG psionics supplements High Psionics: Phrenic Scourges and Psionic Bestiary. (The "psycholus" is a monster with a similarly freakish appearance that was featured in psionics supplements by Daemoneye Publishing, but is not based on the scourge.)
• Possessor. Originally appeared in Possessors: Children of the Outer Gods by Ronin Arts. They appeared as flying octopuses which could engulf a person's head to control them. They were greatly expanded on by Bad Axe Games in Slavelords of Cydonia as the "lethid." Both the phrenic scourge and possessor were reprinted/converted in Forgotten Foes by Tricky Owlbear Publishing/Fat Goblin Games. 

There were a number of others, but none received as much attention as these did. I took a few of the other substitutes (paretiophage from Minions series by Bastion Press, mindolon from Edition Pi by Daemoneye Publishing, and brilkoun from Monster Geographica) and combined them with the classic intellect devourer to create an all-purpose brain-eating monster family.

This gives me four families of monsters that substitute for the iconic mind flayer. Fun!