The main villain/monster for Stranger Things 3 is the Mind Flayer. Named after the Dungeons & Dragons monster, the Mind Flayer is a monster that possesses a host, and uses its body as a vessel to carry out its evil. Billy is the main vessel in this latest season, and the Mind Flayer, through him, possesses a number of people (most of whom are eventually turned into flesh goo), including Heather Holloway, his fellow lifeguard, Tom Holloway, Heather's father and the editor of The Hawkins Post, and Doris Driscoll, an old lady who tells Nancy about the infected Rats. Oh yeah, that's right—the Mind Flayer possesses and melts down a whole lot of rats. Though Vecna's control of the Mind Flayer's hive mind made him powerful, the two-way nature of the psychic connection was also a point of vulnerability. Any pain felt by the connected entities was shared amongst them; the physical suffering of his thralls would translate to every other being in the hive mind, including Vecna himself. This made the hive mind a prime target for his enemies. A rare and most treasured item in a mind flayer colony was a flying ship known as a nautiloid. [2] Mind flayers once had a massive presence in space and commanded countless of these conch-shaped spelljammers. In fact, spacefaring mind flayers were sometimes quite different from their land-bound counterparts and acted more as traders than conquerors. [43] [45] However, incessant hunting by the gith and the fact that mind flayers lost the means to build them or acquire them from the arcane caused them to almost disappear. [2] [46] Religion Mind flayers constantly experimented with transforming other creatures and implanting their tadpoles into different races, producing a large variety of thralls. [2] [65]

While speculating the shadow monster's weakness, Lucas, Mike, Dustin, and Max theorized that if they destroyed the monster, they would also destroy the monster's army. When they realized that the shadow monster controlled everything in a hive mind, they compared it to the Mind Flayer, a monster from Dungeons & Dragons that similarly controls the minds of its victims. The boys' D&D manual also stated that the Mind Flayer's goal was to spread and take over other dimensions, making them speculate that the shadow monster wanted to do the same. The group decided to interrogate Will to find the shadow monster's weakness. As a race of planar travelers, mind flayers did not worship entities from the Outer Planes as deities and did not share the same mythical thoughts about the afterlife. [47] [2] Furthermore, the illithids did not believe they possessed souls; [2] nevertheless, they could still become petitioners, [48] but their disinterest in such a conception of life after death made such petitioners rare, [8] and those in their primary patron's realm appeared and acted much the same as their living counterparts. [48] Said souls most likely initially belonged to the tadpole that created the mind flayer, as the host's original soul was either sent to the Fugue Plane or destroyed completely after the process of ceremorphosis was complete. In fact, the former Lord of the Dead Jergal, and also Mystra, stated that the souls of mortals disappeared after they became mind flayers. [13]A smaller sect of mind flayers revered another entity called Maanzecorian. It embodied a complete comprehension of knowledge and the simultaneous access to memory, thought, and aptitude. [2] It was also viewed by the illithids as a keeper of secrets. Its essence was killed by Tenebrous, the undead shadow of the demon lord Orcus sometime in the mid-14 th century DR, [52] though this fact was unknown to most at the time. [53] However, in the late 15 th century DR, mind flayer colonies dedicated to Maanzecorian were again common. [2] Eric L. Boyd (November 1998). Demihuman Deities. Edited by Julia Martin. ( TSR, Inc.), pp. 13, 18, 26, 33, 54, 57, 71, 129, 143. ISBN 0-7869-1239-1. To non-illithids, mind flayers seemed calm and collected at almost all times, dispassionate and seemingly emotionless outside of their constant desire to dominate others. [23] [33] They dismissed basal emotions like pride as fatal flaws and founded themselves on a pragmatic outlook. [30] While they might occasionally seem furious, it was difficult to discern if this was actual feeling or a ruse to manipulate others. Theories on this ranged from the belief that the mind flayers had no emotions, very few, or extreme levels of self-control, but all of these were incorrect. In truth, illithids had a whole spectrum of emotions and felt them intensely, [23] [33] sometimes even behaving irrationally because of them, [30] but these feelings were almost entirely internalized and not evident even during moments of raging inner turmoil. [33] A silver crown levitated above Maanzecorian's head with a gem of brightness embedded inside, though the light had no ill effects on illithids. [6]

Bruce R. Cordell (April 1998). The Illithiad. Edited by Keith Francis Strohm. ( TSR, Inc.), p. 40. ISBN 0-7869-1206-5. As Chief Hopper remarked, the hub appeared to be a "graveyard" of sorts; dead and decomposing bodies of animals were strewn across the floor. The hub also appeared to contain piles of shedded Demogorgon skin. Bruce R. Cordell (April 1998). The Illithiad. Edited by Keith Francis Strohm. ( TSR, Inc.), p. 41. ISBN 0-7869-1206-5.After the fireworks fizzled out, the proxy monster regained its composure; it launched a spiked tendril directly at Eleven, only to be intercepted by Billy. The creature, enraged by Billy’s betrayal, launched a dozen more tendrils at him, fatally wounding him. At the same time, Hopper and Joyce reached the Soviet control room and disabled the Key machine. Hopper was thought to have perished in the process, but had survived by escaping to another platform within the same room. He was soon captured by Soviet forces. Maanzecorian appeared as a 10‑foot-tall (3‑meter) illithid with purple-green skin and yellowed tusks on the sides of his tentacles. [6] Personality [ ] As an abstract, Maanzecorian was considered narrower in scope than Ilsensine, who embodied psionic union with the self and the realm of universal knowledge. Maanzecorian represented the ideal of total understanding, a state in which one's thoughts, experiences, and innate talents were all simultaneously brought to the forefront rather than conceptualized one at a time as needed. Mind flayers that emulated Maanzecorian had long been fascinated by the perfect memories of the aboleths, [4] who possessed a racial memory that passed from one generation to the next and could always be flawlessly remembered, [17] leading to frequent conflict between the two races. [4] Clergy [ ]