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This article is about the entity. For the episode, see The Mind Flayer (episode).

The Mind Flayer, also known as the Shadow Monster,[1] is a malevolent entity that rules the parallel dimension known as the Upside Down. He was introduced in Stranger Things's second season and serves as the main antagonist of the series.

The Mind Flayer is a massively powerful being of unknown origin. He wields supreme control of the Upside Down, as well as the Demogorgons, Thralls, tendrils and the Flayed. With murderous intent, he repeatedly attempts to corrupt both Hawkins and the wider world.

The Mind Flayer first began his conquest to take over the world in 1984 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.

The part of the Mind Flayer remained dormant until it was reawakened in 1985 by the Hawkins Key. It then began flaying multiple humans and rats, feeding them chemicals, and melting their bodies into puddles of biomass that would be used to create a new body for itself to take over the world. The Mind Flayer nearly succeeded in his plan, but was killed when Joyce and Hopper snuck into the secret Russian laboratory and closed the new gate, severing the connection once again.



The history of the Mind Flayer prior to October 1984 remains a mystery. Exactly how long he had existed for, and how and why he came into inhabit the Upside Down, is unknown. The Mind Flayer's ultimate goal and why he constantly tries to enter our world is also unclear.


In November 1983, an inter-dimensional gate was opened at Hawkins Lab, allowing the Upside Down to begin to spread through. It is not known if the Mind Flayer was present within the Upside Down at this time.

Will Byers, a young resident of Hawkins, was captured by a Demogorgon and brought to the Upside Down's version of the town's public library. Although he was safely recovered by friends and family, Will began to have visions of the Upside Down.


Visions of the Shadow Monster

Will continued to have visions of the Upside Down for a year following his rescue. These visions were examined by Dr. Sam Owens at Hawkins Lab, who believed Will was experiencing post-traumatic stress disorder.

On October 29, 1984, Will and his friends went to play at the Palace Arcade. While his friends argued with the arcade's employee, Will became distracted by another vision. He walked out of the Upside Down version of the arcade. To his horror, he witnessed a blood-red storm raging in the sky above, before hearing an unearthly howl. However, Will's friend Mike snapped Will out of the vision.


A drawing of the Mind Flayer, drawn by Will Byers.

Will had another vision the following evening. He went to have a bathroom break in the middle of the night, and was returning to his bedroom. However, he saw a red light illuminating the walls of his house. The front door swung open, revealing the Upside Down beyond it, where the red storm violently raged once again. Will walked out into the Upside Down and witnessed the obscured but distinctive silhouette of the Mind Flayer amongst the clouds.

On Halloween night, Will experienced yet another vision while trick-or-treating in Loch Nora, a wealthy neighborhood in Hawkins. He found himself in the Upside Down version of the neighborhood. At first, Will heard a strange chittering sound coming from multiple directions. Then, he watched in horror as the Mind Flayer rose high into the air before pursuing him through Loch Nora. Will hid behind a wall, unaware that the creature was close behind him. However, Mike found Will and snapped him out of the vision before the Mind Flayer could touch him.

Will's next vision took place at school, shortly after he encountered Dart in the bathroom. Will found himself in the Upside Down once more, standing in the school corridor. Suddenly, the Mind Flayer's dark mist began to flood into the corridor before chasing after Will. After running outside and onto the field, Will stopped and turned to see the Mind Flayer looming high above the school. Remembering what Bob had told him as they drove to school, Will attempted to confront the Mind Flayer, yelling at him to "go away!" The Mind Flayer ignored Will, continuing to pursue him before entrapping him within one of its tornado-like appendages. From that point on, the Mind Flayer began to slowly take over Will's mind and body.

The Invasion

As time passed, Will's connection with the Mind Flayer deepened, making him frightened and distraught. Fortunately it led Will, Joyce, Bob and Mike to finding the location of Hopper and rescuing him at the tunnels. However, due to his being a part of the hive mind, he experienced severe agony following the burning of the tendrils. It enraged the Mind Flayer as referred by an ailing Will and as retaliation, the Mind Flayer deceived Will into revealing a location that it was afraid of and exploited their connection to use him to massacre the scientists at the Hawkins Lab.

The Three-Fold Assault

In the fallout of the Hawkins Lab massacre, the Mind Flayer escalated his conflict with the human world. Unleashing countless Demodogs into the underground tunnels, the Flayer seemed hell-bent on destroying his enemies.

Meanwhile, the assembled allies retreated to the Byers house. They isolated the compromised Will in a dark room to stop the Flayer from spying any further. The allies discussed the nature of the Mind Flayer and the Upside Down in a desperate bid to defeat him. As with the Demogorgon, the kids used a Dungeons & Dragons-based analogy to theorize about the Flayer's nature; and thus, the nickname "Mind Flayer" was born.

The first wave of Demodogs arrived at the house, but as they did, so did Eleven. El fended off the Dogs, and after reuniting with her friends, the allies developed a three-fold plan of action against the Mind Flayer. All three of the following events unfolded more or less simultaneously, but all collectively contributed to the Flayer's defeat:


The allies attempted to free Will from the Flayer's influence, and thus return him to his former state. Although these attempts largely failed, Will mentally fought back against his captor and regained control of his left hand. He began to tap the side of his chair in Morse Code, which, when translated, revealed the message "CLOSEGATE". The allies realized what had to be done, sending Eleven and Hopper on a mission to close the doorway between worlds.

The pair arrived at the now-abandoned laboratory, and as they descended through the vast depths below, the Mind Flayer's huge silhouette loomed behind the other side of the Gate. The Flayer sent one of his many coils through the barrier in an attempt to stop her while simultaneously commanding Demodogs to attack them.

However, Hopper managed to fend off the Dogs, while El used her powers to neutralise the coil. Finally, Eleven channeled her anger and closed the Gate, sealing the Flayer's main form back inside the Upside Down. Sealing the Gate also cut off the Demodogs' connection to the Flayer, killing them all almost instantly; even Dart could not survive.

The Exorcism

Joyce, Jonathan and Nancy attempted to "exorcise" the Mind Flayer from Will's mind and body. They did this by exposing Will to extreme heat, even burning his arm with a fire poker. The possessed Will initially resisted, writhing and shrieking in pain, but eventually, the fragmented Flayer could no longer stand the heat. He fled the body and flew far, far away into the night sky. This ethereal fragment of the Flayer would eventually reawaken at Brimborn Steel Works.

Distracting the Dogs

At the last minute, Dustin, Lucas, Max, Mike and Steve made a plan to distract the Mind Flayer, and thus diverting his attention from the events involving Eleven and Will. They headed to the subterranean tunnels, soaking "The Hub" with gasoline and setting it aflame. This further weakened the Mind Flayer's grip on Will, as well as drawing some of the Demo-Dogs away from the Gate and Eleven.


With the Demodogs eradicated and the Gate sealed, the human world unknowingly enjoyed a quiet victory. With the telepathic link to his main form in the Upside Down severed, the ethereal fragment of the Mind Flayer that left Will's body became isolated and dis-empowered. This fragment form would lay dormant at Brimborn Steel Works for over seven months, until the events of July 1985.

In December, during the Snow Ball at Hawkins Middle School, the Mind Flayer loomed over the version of the school in the Upside Down, seemingly spying on Eleven from across dimensions.


In the summer of 1985, a secret Russian operation located beneath Hawkins' newly-built Starcourt Mall successfully opened another Gate into the Upside Down. Unlike the first Gate, the new breach was too small to let through creatures and vines; however, it was still wide enough for the Mind Flayer to renew his telepathic link with the isolated piece of himself at Brimborn Steel Works. He used this fragment form to "infect" the rats inhabiting the Steel Works and other underground areas around Hawkins, causing them to consume fertilizer, gather in swarms within the Steel Works, and then explode into blobs of biomass. The biomass fused together with the fragment form into a creature with the approximate shape and proportions of the Mind Flayer's main form. This monstrous creature served as a proxy body, through which the Mind Flayer could once again influence events in Hawkins.

Later, the Mind Flayer caused Billy to crash his car, which got him to investigate the Steelworks, only to get captured and become his main host. He uses Billy to capture Heather and make her become one of the Flayed. They both later capture Heather's parents Janet and Tom. Doris Driscoll also became part of the Flayed, likely from the rat she captured. Others become part of the Flayed, including Bruce (likely from Tom, other members of the Hawkins post may have been Flayed as well), a man named David, and a kid named Adam become part of the Flayed at an unknown time. Will later mentions that the Mind Flayer is back, and it is eventually discovered he is controlling multiple people.

When Eleven tries to find the Mind Flayer's location through Billy, the Mind Flayer ends up talking to her through Billy's body in a Mindscape version of Hopper's Cabin. Knowing her location, the Mind Flayer melts the Flayed (except for Billy) and absorbs them to become stronger. He then goes after Eleven and attacks the cabin, managing to knock Jonathan against a wall and bite Eleven. She responds by tearing the Mind Flayer's head in half, forcing him to regenerate which leaves him temporarily unable to pursue them. Eleven feels the effects of the bite, but removes the piece of the Mind Flayer that was inside her leg.

Incarnations & Appearance

The Shadow Form

The Mind Flayer is a gargantuan entity, being at least 50 stories tall. The details of his anatomy remain unclear, due to the thick, silver-black mist which envelops him. It is unclear whether he is entirely composed of this substance, or if his body contains any solid elements. The creature has multiple limbs, some of which branch into several smaller appendages; these limbs visually resemble the tendrils and vines present in the Upside Down. He seems to have an elongated, flame-shaped head which sprouts from the central body. His presence is often accompanied by unnatural red lightning, which Will describes as a "storm".

Through his telepathic link, the Mind Flayer could directly control additional entities and beings:

The Isolated Fragment

Pockets of the silver-black mist could move independently while remaining under the control of the Mind Flayer. One of these pockets left the main body and latched itself onto Will Byers, allowing the Mind Flayer to possess him. Will's friends and family eventually forced the creature to abandon Will, with the mist fragment flying away into the sky. The mist fragment eventually re-awakened at Brimborn Steel Works when the Starcourt Key was activated in the Summer of 1985, renewing the mist fragment's telepathic link to the main body. The Mind Flayer, via the mist creature, immediately summoned hordes of rats to the Steel Works, melting down their bodies and creating the Proxy Body.

The Proxy of 1985

The Mind Flayer's 1985 proxy body resembled a gargantuan, monstrous spider. This incarnation of the Flayer closely matches its Upside Down counterpart in terms of its shape and proportions. However, unlike the Flayer's main body, his Proxy is not shrouded in silver-black mist, nor is it as large (though it still stands tall at over 20 feet in its fully-formed state). The Proxy is nigh on indestructible, but remains vulnerable to heat.

The Proxy body is composed of the bodies of the Flayed: dozens of congealed organisms, both human and animal, who were converted to serve the Flayer's will. The Proxy was originally relatively small, being composed purely out of Flayed rodent bodies; however, he rapidly grew into his fully-fledged state after finally consuming the converted humans.

The Flesh Thralls

Additionally, the Mind Flayer can form smaller monstrosities under his control, which can later be re-absorbed into the Proxy. Examples of these include the Hospital Creature and the Bite Blob. Like the Proxy, the Flesh Thralls are composed of Flayed humans and animals.


The Mind Flayer is a sentient entity that possesses intelligence equal or superior to that of a human. This sets him apart from the Demogorgons, which appear to behave purely animalistic when he is not exercising its control over them. The creature was highly hostile toward anyone and anything that threatened its plans; using its almost omni-potent intelligence and dominion over the Upside Down to its advantage, it would develop ways to thwart and outsmart its adversaries. Such as, using its possession over Will as a way to spy on Hawkins Lab and luring a team of soldiers into a trap.

While much of the Mind Flayer is currently shrouded in mystery, through Will’s connection to the entity, it is known that the Mind Flayer sought to eradicate humanity. While its true motivations for doing so are yet to be determined, through comparing the entity to the synonymously named creature from Dungeons & Dragons, Dustin theorized that the Mind Flayer viewed himself as superior to all other life. Exactly how accurate this theory is remains to be seen.

While a massively powerful being, the Mind Flayer was not without its weaknesses. Most notably, he has a low tolerance to heat. All hosts within its hive mind share this weakness, resulting in him feeling pain whenever a host is exposed to heat or burned.


  • Hive Mind: The Mind Flayer's most distinctive feature is the ability to take control and command of the creatures from the Upside Down and later Will. Upon having its feeding area burned, he sent multiple Demodogs to the tunnels in order to deal with the problem. He also had them try and stop Eleven from closing the Gate. The downside of this mental connection was that the burning of tendrils would affect the Demodogs and Will, and most likely the Mind Flayer itself. Will was also able to learn instinctive knowledge of its goals, the tunnels and weakness. Despite the hive mind's reach, when Eleven sealed the rift between worlds, the connection was severed and led to the death of its subjugates.
  • Possession: By imbuing a portion of its essence on an affected subject (despite both the Mind Flayer and Will being in separate worlds), the Mind Flayer is able to link the infected to the rest of its army. An example of its power was how he tricked Will into sending numerous soldiers to their death by having Will tell them its weakness was within the feeding area in the tunnels. The possession can be severed by subjecting the infected to extreme heat, which burns the essence out of its body by making it uninhabitable due to a weakness to heat and light. However, when a host is under threat of being discovered or severed from the Mind Flayer's possession, its influence can force the host to fight back; it gave Will inhuman levels of strength, allowing him to remove its restraints and throttle Joyce effortlessly with one hand while she attempted to free Will from the creature's possession.
  • Biokinesis: Through sheer force of will it can melt host bodies and maintain a proxy body, though this ability appears to be fairly limited as the Flayed need to be in close range to its main proxy.
  • Weather control: The Mind Flayer is often surrounded by red electrical storms. While the nature of these storms is not entirely clear, it is possible the Mind Flayer is responsible for their creation.
  • Power negation: After biting her with one of its tentacles, the Mind Flayer's proxy left a piece of itself inside Eleven, severely weakening her telekinesis later that evening. Even three months after defeating the creature, Eleven's powers were not back to full strength.


Ever since Eleven closed the gate in front of it in 1984, the Mind Flayer held a deep-seated grudge against her, viewing her as a threat to its plans and creating an army for the sole purpose of destroying her.

Upon its return to Earth, the Mind Flayer lured Billy into its new lair, converting him into the first Flayed and using him to turn other residents of Hawkins, as well. The Mind Flayer did not seem to care for Billy as a person and quickly killed him after Billy broke free from its control through the memory of his mother.

Behind the scenes

Concept and design

Matt Duffer told Entertainment Weekly that the shadow monster was inspired by horror classics: "There's an H.P. Lovecraft sort of approach, this inter-dimensional being that is sort of beyond human comprehension."[2]

Flayer concept art

Concept art of Will confronting the Mind Flayer on the field.

Visual-effects producers Paul and Christina Graff were tasked with designing the creature. Because the first season incorporated several electrical interferences, they knew the second season would involve storms. Once it was decided that the monster was going to be “storm-like”, the Graffs began looking to references of storms and tornadoes. Steve Messing, a matte painter who was also consulted on the designs of several other Stranger Things elements, created concept art of the creature based on tornadoes, volcanoes, and other natural forces. In addition, they were inspired by volcanic eruptions with lightning storms in South America.[3]


While the entity had been referred to as the Shadow Monster throughout production, the Duffers eventually decided to give him a proper name. Looking through the Dungeons & Dragons manual, they decided to name the creature after the Mind Flayer due to how similar it was to their concept for the Shadow Monster.[4]


  • It's possible that to be infected, one needs to have a tendril similar to the Library Tendril attached to them first, or have been in the Upside Down for a significant amount of time; the exact nature of the infection has not yet been confirmed.
  • Possessed humans are colder to the touch than average.
  • Heat and light are one of its weaknesses. Extreme heat causes the human extreme pain, but is able to cure them with enough exposure and heat. Bob Newby also noted that the Mind Flayer's vines beneath Hawkins deliberately avoided contact with bodies of water, meaning it is also likely hydrophobic with an allergy/aversion to water.
  • Both Dart and Will showed the ability to fight or ignore the Mind Flayer's influence. Dart was able to remember Dustin and Will was able to communicate in Morse Code while being reached emotionally by his family.
  • In Dungeons and Dragons, Mind Flayers are a race of psychic humanoids with tentacles on their face who eat brains.  They primarily use their powerful psychic abilities to mentally enslave other beings. More recent editions have given the Mind Flayers the proper name "Illithids".
  • The scene in which the Shadow Monster infects or enters Will bears resemblance to similar possession sequences in horror films, most notably in 1973's The Exorcist.
  • A possessed Billy uses "we" pronouns to refer to itself, suggesting that the Flayed may maintain vestigial traits of individuality even while part of the Mind Flayer's hive mind.


View Gallery

Click the above image to view the gallery for Mind Flayer.


  1. "Stranger Things 2: Behind the sequel's big, bad 'shadow monster'" Entertainment Weekly. September 28, 2017.
  2. "Stranger Things 2: Behind the sequel's big, bad 'shadow monster'" Entertainment Weekly. September 28, 2017.
  3. "How Stranger Things 2 Transformed Hawkins Into the Upside Down" Vulture. November 8, 2017.
  4. "The Duffer Brothers Recap Stranger Things 2, ‘Chapter Eight: The Mind Flayer’" Vulture. November 8, 2017
The Upside Down
Locations The Upside DownThe GateHawkinsHawkins National LaboratoryPublic LibraryPortalsHawkins Middle SchoolHawkins Tunnel System
Entities D'ArtagnanThe DemogorgonDemogorgon (species)The Mind FlayerSlug-like creatureHawkins Tunnel SystemVinesHospital CreatureThe FlayedThe Flesh Thralls
The Flayed Billy HargroveHeather HollowayBruce LoweTom HollowayJanet HollowayDoris Driscoll
Visitors Joyce ByersWill ByersElevenSteve HarringtonDustin HendersonBarbara HollandJim HopperMax MayfieldBob NewbyShepardLucas SinclairMike WheelerNancy Wheeler
Miscellaneous Upside Down EggDungeons & DragonsThe VoidThe Keys
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