Illithids believe themselves to be the dominant species of the multiverse and use other intelligent creatures as thralls , slaves, and chattel. Illithids are well known for making thralls out of other intelligent creatures, as well as feasting on their brains. Mind flayers were created by Gary Gygax , who has said that one of his inspirations for them was the cover painting of the Titus Crow book The Burrowers Beneath by Brian Lumley.
The Mind Flayer
Their natural psionic abilities also made mind flayers respected in the eyes of the drow , beholders , duergar , and other dominant races of the Underdark. Mind flayers were humanoid in appearance but with an octopus-like, ridged head with four tentacles surrounding a lamprey-like mouth. Their hands had long, reddish fingers and lacked the index finger,   and their feet were two-toed and webbed. Mind flayers that were healthy from brain-rich diets excreted a kind of slimy mucous substance that coated their mauve skins. Mind flayers were tyrants, slavers, and planar voyagers. They viewed themselves as masterminds, controlling, harvesting, and twisting the potential of other creatures to further their evil and far-reaching goals. Mind flayers were aggressive and elitist and would attempt to mentally dominate any non-slave, non-illithid that they met.
The Mind Flayer , also known as the Shadow Monster  , is the main antagonist of Stranger Things , introduced in the second season. He is a malevolent entity that rules the parallel dimension known as the Upside Down. The Mind Flayer is a massively powerful being of unknown origin. He wields supreme control of the Upside Down, as well as the Demogorgons , tendrils , and the Flayed. The Mind Flayer first began his conquest to take over the world in when he used the Gate to spread the Upside Down's toxic biological growth underneath Hawkins, as well as possessing Will Byers and an army of Demodogs to take down Hawkins Lab. Eleven ended his plan by closing the Gate and severing the connection between the two worlds but left a part of the Mind Flayer trapped within the human world.
Illithids believe themselves to be the dominant species of the multiverse and use other intelligent creatures as thralls , slaves, and chattel. Illithids are well known for making thralls out of other intelligent creatures, as well as feasting on their brains. Mind flayers were created by Gary Gygax , who has said that one of his inspirations for them was the cover painting of the Titus Crow book The Burrowers Beneath by Brian Lumley. Here, the mind flayer is described as "a super-intelligent, man-shaped creature with four tentacles by its mouth which it uses to strike its prey. A mind flayer's major weapon is given as the Mind Blast, a 5-foot radius wave of "PSI force" which affects each opponent differently based on how intelligent it is; possible effects include permanent insanity, rage, confusion, coma, and death. The mind flayer appears in the first edition Monster Manual The article "The Sunset World" by Stephen Inniss in Dragon October presented a world that had been completely ravaged by mind flayers. The "Dragon's Bestiary" column, in the same issue and by the same author, described the illithidae , the strange inhabitants of this world. The mind flayer appears first in the Monstrous Compendium Volume One ,  and is reprinted in the Monstrous Manual