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Spoiler Warning!
This article or section reveals details from Stranger Things: The First Shadow. Read at your own discretion...
This article is about the entity. For the episode, see "The Mind Flayer". For this entity's proxy incarnations, see The Spider Monster or Hospital Monster.

The Shadow Monster, the particles, and the Mind Flayer were all names used to describe a shadowy entity that originated from an unknown alternate dimension. The entity appeared to entirely consist of silver-black particles linked together through a group intelligence.

The entity was gigantic, looming at least fifty stories tall[1] and sporting a distinctive spider-like appearance. The Mind Flayer exercised supreme control over the Upside Down via a psychic link, with Demogorgons, vines, and Demobats forming a shared hive mind; for a period in 1985, possessed humans known as "the Flayed" also comprised part of the hive mind. This meant the entirety of the Upside Down was essentially like one gigantic organism, with all its contents and agents mentally connected via the Mind Flayer.

The entity’s first known encounter with humanity occurred in the 1950s, when a young child named Henry Creel was accidentally transported to Dimension X and exposed to the entity’s influence; upon returning home, Henry found he had gained special psychokinetic abilities, but was also vulnerable to the entity’s influence, making him use his powers to commit violent acts. Years later, in 1979, Creel once again found himself in Dimension X and encountered the shadowy entity once more, though he appeared to have no memory of the earlier event. This time, Henry used his powers to reconstitute the mist into a form that satisfied him: a giant, spider-like entity with a flame-shaped head.[2][3]

In 1983, a gate to the Upside Down - a dimension somehow related to Dimension X - was accidentally opened by Eleven at Hawkins Lab. Henry, also known as Vecna, first actively attempted to take over the world in 1984. Acting through the Mind Flayer - which had since awakened or materialised within the Upside Down - Vecna possessed Will Byers and an army of adolescent Demogorgons, or "Demodogs". Eleven interfered by closing the gate at Hawkins Lab, severing the psychic link between the worlds and killing the Demodogs in the process. As Eleven closed the Gate, Will's friends and family worked to force a piece of the Mind Flayer out of his body, which in turn became dormant after the Gate's closure.

The isolated piece of the Mind Flayer remained dormant at Brimborn Steel Works until 1985, when a newly opened gate reestablished the psychic link to Vecna. Via this piece, Vecna began kidnapping and possessing multiple humans and rats, feeding them chemicals and melting their bodies into puddles of biomass. This biomass was then combined to create a proxy form, through which Vecna could directly act in the human world; like the Mind Flayer, this proxy form also resembled a spider, and had the same flame-shaped head. However, this proxy form was rendered useless and inert after the new Gate was shut, and the psychic link disabled once again.[4]

In the same time period, the Soviet Union somehow captured a portion of the Mind Flayer's particles and stored them at a military base in Kamchatka, along with an adult Demogorgon and a number of paralysed Demodogs. Hopper, Joyce and Murray escaped the base in March 1986, but returned to destroy the Mind Flayer's particles, hoping to aid their allies in Hawkins by inflicting damage to the Upside Down's hive mind. However, upon their return, they discovered that the particles had escaped confinement and possessed the bodies of the paralysed Demogorgons, freeing them. They were forced to change their plans, aiming to kill the Demogorgons instead, as doing so would also destroy fragments of the Mind Flayer, and weaken Vecna in the process.

Quick Answers

What is the origin of the Mind Flayer in Stranger Things? toggle section
The Mind Flayer in Stranger Things is a malevolent entity from the Upside Down and serves as one of the main antagonists of the series. It's a hive-minded creature that can possess and control people, much like the possession sequence in the 1973 film, The Exorcist. The Mind Flayer's concept is very similar to the Elder Gods of H.P. Lovecraft's works, suggesting a possible inspiration for its creation.
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What is the relationship between the Mind Flayer and the Demogorgons? toggle section
The Mind Flayer and the Demogorgons from Stranger Things share a unique relationship. They are all part of a hive mind, meaning they are interconnected and act according to the same collective consciousness. The Mind Flayer, being a malevolent entity from the Upside Down, uses this hive mind to control the Demogorgons and carry out its plans. This relationship was particularly evident when the Mind Flayer attempted to eradicate humanity in 1984, using the Demogorgons to execute its bidding.
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What are the other names for the Mind Flayer in Stranger Things? toggle section
The Mind Flayer in Stranger Things is also referred to as the malevolent entity from the Upside Down. It's one of the main antagonists of the series. In some contexts, it's also known as the 'shadow' or the 'Stranger Things season 2 monster'.
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What is the physical appearance of the Mind Flayer? toggle section
The Mind Flayer, also known as the Shadow Monster in Stranger Things, has a unique and terrifying physical appearance. It has an elongated flame-shaped head and six branching spider-like legs, giving it a vaguely spider-like appearance. The creature's body is highly irregular, with bones from its victims jutting out from various parts of its body. It is equipped with several prehensile tentacles used for offensive attacks, one of which extends from the monster's mouth. The maw of the creature is filled with circular rows of jagged 'teeth'. The Mind Flayer is made up of minuscule particles, giving it a misty appearance akin to a shadow. It also has numerous tornado-like limbs, some of which branch into several smaller appendages, visually reminiscent of the vines that overrun the Upside Down.
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How does the Mind Flayer control the Upside Down? toggle section
The Mind Flayer, also known as the shadow stranger things monster, exercises supreme control over the Upside Down through a psychic link. This link connects all entities within the Upside Down, including Demogorgons, vines, Demobats, and for a time, possessed humans known as 'the Flayed'. This connection forms a shared hive mind, making the Upside Down virtually a giant superorganism. The Mind Flayer can possess other creatures by embedding fragments of itself inside their bodies, further extending its control.
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The Mind Flayer had unclear origins. According to Dustin, the D&D version of the Mind Flayer was "a monster from an unknown dimension", a creature "so ancient that it doesn't even know its true home".[5] Dustin's description seemed to mostly hold true to the real-life Mind Flayer, which also originated from an unknown alternate dimension; however, the entity possibly originated from Dimension X, where it was first sighted.


Following 1943's Philadelphia Experiment incident, in which the USS Eldridge was accidentally transported to Dimension X, Dr. Martin Brenner and his staff began work on the "Nevada Experiment", an attempt to reproduce what had happened to the vessel. The government facility that hosted the experiments was located in or around Rachel, Nevada. However, a rogue staff member defected and stole essential equipment from Brenner, hiding the equipment inside a nearby cave system.[6]

According to one account, it was this equipment which changed the trajectory of Henry Creel's life forever. Henry, who was only a small child, was exploring the Nevada caves one day while playing with his spyglass. While exploring, Henry stumbled across the scientific equipment; the technology unexpectedly activated, transporting Henry and the rogue staff member to Dimension X, killing the staff member in the process. In the alternate world, Henry saw glimpses of strange creatures and was exposed to the influence of a shadowy entity.

Henry survived the ordeal and eventually returned home after 12 hours, but with wildly different blood, and an altered personality. Dr. Brenner later recovered the stolen equipment, also finding the spyglass belonging to Henry. Brenner was able to eventually track down Henry thanks to the dropped spyglass, and would eventually make him the first of a new series of test subjects at Hawkins Lab.

According to this account, it was Henry’s exposure to the shadowy entity that led him to develop special psychokinetic abilities. This appears to contradict Henry's own account of events, in which Henry apparently discovered the Mind Flayer and Dimension X at a much later stage in his life.[6][7]


The discovery

On September 8, 1979, a much older Henry Creel, now an orderly at Hawkins Lab, entered a psychokinetic duel with test subject Eleven in the lab's Rainbow Room. Eleven ultimately overpowered Henry, sending him through a gate to a mysterious alternate dimension ("Dimension X"): a realm defined by mountainous terrain and electrical storms. Henry began to traverse the alien terrain, encountering “so many things”, including a species of faceless humanoid predators. Eventually, Henry discovered “the most extraordinary thing of all”: a dormant, living organism made up of swirling, storm-like particles.[2][3][8]

Birth of the Mind Flayer - S4E9

Henry moulds the mass of mist into the Mind Flayer

Using his abilities, Henry formed a psychic connection to the particles. He used his powers to reconstitute the mist-organism into a form that satisfied him: a giant, spider-like entity with a flame-shaped head (not unlike a similar fantasy creature he had imagined as a child). In time, this being would come to be known as the Mind Flayer.[9]

A familiar figure

When Henry initially encountered the shadowy entity, the entity first - either literally, or just in Henry's visions - adopted the voice and form of Alice, Virginia and Victor before eventually adopting the persona of Dr. Brenner. The entity claimed it wanted to "study" Henry, and that he was the "most magnificent thing" it had ever encountered. The entity encouraged Henry to take control of the various Demogorgons that roamed the landscape, which Henry achieved by systematically penetrating the mind of each individual creature.

Henry and the entity developed a complicated relationship via psychic connection; Henry repeatedly attempted to seize full control over the entity and the hive mind, but the entity would retaliate, forcing Henry to re-experience troubling memories.[10]


The Demogorgon's attacks

On November 6, 1983, the Mothergate opened at Hawkins Lab, allowing the Upside Down - a realm somehow related to Dimension X - to begin to spread through. 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.

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.


Possession of Will Byers

On October 29, 1984, Vecna began acting through the Mind Flayer in his first attempt to conquer the world and exterminate humanity.

That night, 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 Wheeler snapped Will out of the vision.

The following morning, Hopper was called to Merrill Wright's farm to investigate a strange rot that had decimated the entirety of the pumpkin patch.

MADMAX - Will sees the Mind Flayer

Will first sees the Mind Flayer


Will's drawing of the Mind Flayer

Will had another vision later that day. 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, or "shadow monster", amongst the clouds.

On Halloween night, Will experienced yet another vision while trick-or-treating in Loch Nora, finding 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 shadow monster rose high into the air before pursuing him through the neighborhood. 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 shadow monster could touch him.

The next day, Hopper told Owens that the lab must investigate the rot that decimated Merrill's pumpkin patch, suspecting it was tied to the Upside Down. Owens initially resisted, insisting the breach was "contained", but eventually acquiesced to Hopper's demands. Upon extracting and experimenting upon the soil from the pumpkin patch, Owens were shocked to learn much of the soil seemed to come alive when exposed to heat, each sample forming a swirling, silver mass of particles trapped within various beakers.

S2E3-Mind Flayer reaching

The entity reaches an 'arm' out to Will

Mind Flayer possessing Will

The particles possess Will

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 shadow monster'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 shadow monster looming high above the school. Remembering what Bob had told him as they drove to school, Will attempted to confront the shadow monster, yelling at it to "go away!" The shadow monster ignored Will, continuing to pursue him before entrapping him within one of its tornado-like appendages.

From that point on, Will gradually became possessed by the shadow monster. His body temperature dropped and he developed an aversion to heat. He also began experiencing what he called "now-memories", where he could see and know what the shadow monster did. In order to better explain his now-memories, Joyce asked Will to draw what he saw. He began frantically drawing what at first appeared to be random scribbles, but Joyce and Hopper soon realized that the drawings were all connected. After assembling the drawings in the correct order, they discovered the drawings depicted a strange maze-like pattern.

Believing the drawings to depict the Upside Down's vines, Hopper went back to Merrill's pumpkin patch. By digging into the earth, Hopper discovered the existence of the underground tunnels, overgrown with vines and other organic material from the Upside Down. While traversing the tunnels, Hopper became entrapped in vines, unable to escape. Will learned of his predicament through his connection with the shadow monster, and with the help of Bob Newby, they were able to pinpoint his location within the tunnels. After Joyce and Bob successfully freed Hopper, soldiers from the lab arrived and urged them to leave. As the soldiers began burning the tunnels, Will suddenly collapsed and began convulsing on the ground.

Chapter Six - The Spy

Dr. Owens inspects Will at Hawkins Lab

Will was taken to the lab were he was quickly sedated. When Will awoke, he could not remember Owens, Bob, or Hopper, and was barely able to remember Mike. In a test involving a severed vine from the Upside Down, Owens asked if Will could feel anything as another scientist used a blowtorch to burn the vine. Through this, they determined that Will had some sort of “virus” that connected him to all other infected hosts in a hive intelligence.

Using the Demodogs

Claiming he knew of a way to beat the shadow monster, Will pointed out a location in the tunnels, saying "he doesn't want me to see there." As the soldiers entered the tunnels, Will revealed that the shadow monster had forced him to deceive them. The soldiers were ambushed and killed by a pack of adolescent Demogorgons called "Demodogs". Shortly after, Demodogs began invading the lab. While the group was escaping the lab, Bob was tackled and killed by several Demodogs. Everyone else, excluding Owens who had stayed behind, managed to escape the lab.

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.

After making the backyard shed unrecognizable, they placed Will inside and attempted to interrogate him. While the Mind Flayer had taken over a majority of Will's mind and body, a part of Will managed to subconsciously signal to them in Morse code. Deciphering his message, they discovered how to stop the Mind Flayer: they had to close the Gate. Soon after, the phone in the Byers' kitchen rang, giving away their location. A pack of Demodogs quickly surrounded the house, but before they could attack, Eleven arrived and eradicated the creatures.

Closing the Gate

After taking Will to Hopper's cabin, Joyce, Nancy, and Jonathan restrained him, surrounding him with numerous heaters. This eventually caused the fragment of the Mind Flayer possessing Will to be expelled from his body. The particles fled the cabin, escaping to the abandoned Brimborn Steel Works to lay low.

Eleven closes the Mothergate

Eleven closes the Gate

Mind Flayer hovering the Hawkins Middle School

The Mind Flayer looms above Hawkins Middle

Hopper guided Eleven through the lab to the Gate, so that she may finally close it for good. Drawing on all her strength and pain, Eleven successfully used her powers to seal the rift. Vecna and the Mind Flayer's psychic link to the human world was cut off, causing the Demodogs and the tunnel-organism to die. The particles of the Mind Flayer’s fragment scattered across the floor of Brimborn Steel Works: dormant, but not destroyed.

On December 15, during the Snow Ball, the Mind Flayer loomed over the Upside Down version of Hawkins Middle School, sensing Eleven's presence on the other side.


Main article: The Spider Monster

The Soviets' gate

On June 28, 1985, a secret Russian operation located beneath Hawkins' newly-built Starcourt Mall successfully opened another Gate into the Upside Down. Soviet-owned properties in East Hawkins, all near transformers, were used to siphon off energy from the town's power grid, triggering a major power outage. The energy was redirected to the underground base, and channelled into the Key. The Key ray activated and fired into the base wall, with a gate successfully forming. In the days that followed, the Soviets were able to acquire creatures and genetic material from the Upside Down; they even captured a fragment of the Mind Flayer and a pack of Demodogs, which were incapacitated and shipped to a facility in the Kamchatka Peninsula. The Demodogs were kept paralysed in tanks filled with oxygenized water, and the Mind Flayer fragment was entrapped in a special cell covered with heating devices in the facility, directly adjacent to the room containing the Demodogs.[11]

The Flaying

The melting rats

Rats gather at the Steel Works

S03E02 Official Image

Billy sees the Upside Down

After the gate was successfully formed, the Upside Down's psychic link to Hawkins was also re-established, reviving the fragment of the Mind Flayer laying low at Brimborn Steel Works. The cloud of particles began possessing hordes of rats, and had them consume different types of chemicals; many of the rats would then explode into bloody puddles of biomass to create a proxy form, through which Vecna (via the Mind Flayer) could operate in the human world.

While driving down Cherry Oak Drive, Billy Hargrove suddenly found himself attacked by an unseen force, causing him to crash his car. Billy left the vehicle to investigate, coming across the abandoned Steel Works nearby; suddenly, a giant tendril emerged out of nowhere and dragged Billy into the shadows. In the basement of the Steel Works, the rat-flesh creature pumped toxic material into Billy's face and infected his mind, converting him into an obedient servant. Billy hallucinated himself leaving the building, only to find himself in the Upside Down; he saw a number of shadowy figures appear in the distance, and tried to call out to them. One of the figures walked forward; Billy was shocked to realize he was looking at a mirror image of himself who told to "build what he saw".


The possessed Billy's eye formulating black veins

The next day, a mind-addled and disturbed Billy kidnapped his co-worker Heather Holloway and took her to the Steel Works, where she too became possessed by the creature. Over the next few days, dozens more people were 'Flayed', including Doris Driscoll and Bruce Lowe. The Flayed would often target those close to them, such as Heather's parents, Tom and Janet. In some cases, such as with Doris Driscoll, exposure to infected rats was enough to bring the individual under the Mind Flayer's thrall. As with the rats, the unfortunate humans would be made to gorge cleaning fluids and other toxic chemicals, which would seemingly boost the infection's grip upon their minds. Some of these individuals would later dissolve into biomass, and reconstituted into fleshy monstrosities directly under the hive mind’s control.

Eleven and her friends began investigating Billy after they realised he had been acting strange; after confronting him at the Hawkins Community Pool, the group realised he had fell under the Mind Flayer’s control. Later, Eleven used psychic projection to locate Billy after he escaped their encounter. However, to Eleven’s surprise, Vecna was aware of her presence within Billy's mind, and placed her in a hallucination; using Billy as a vessel, Vecna talked to Eleven and learned of her location. However, in this moment of psychic connection between Eleven, Billy and Vecna, Eleven also saw Billy’s childhood memories, and learned of his troubled past.[4]


The Tom-Bruce amalgam

Meanwhile, Vecna had the Mind Flayer melt down the bodies of the Flayed; a new monster was created from the melted remains of Tom Holloway and Bruce Lowe, which in turn merged with the proxy creature at the Steel Works. Eventually, all of the Flayed were summoned to the Steel Works, where all except Billy were melted and absorbed into the rat-flesh creature. The giant spider-like creature, not dissimilar in appearance to the "shadow monster", broke threw the roof of the Steel Works and began to hunt down the Party, knowing they were at Hopper’s cabin. the Party and their allies were viciously attacked, but largely succeeded at defending themselves; however, a small piece of the proxy monster detached itself and bit into Eleven's leg, severely wounding her.

The battle of Starcourt Mall

Later that night, Eleven's group went to Starcourt Mall to find Dustin, who had apparently located a new gate to the Upside Down. Shortly after meeting with Dustin and his friends in the food court, Eleven suddenly writhed in pain and fell to the ground; the group realised a piece of the flesh creature was still embedded in her wound. Jonathan forced the creature out, escaping before being dramatically crushed underfoot; Hopper, Joyce and their friend Murray Bauman had arrived at the mall, who hoped to infiltrate the Russian base and destroy the gate. Taking what Dustin, Steve, Robin Buckley and Erica Sinclair had learned from their own adventure inside the base, Hopper, Joyce and Murray travelled there via the secret elevator their younger allies had discovered. After gunning down various Soviet soldiers, the trio took and donned their military uniforms, going incognito as they entered the facility.

In the food court, Eleven was unnerved to discover she had seemingly lost her psychokinetic abilities, leaving her and her friends vulnerable to the monster's attack. Not long after, Billy and the flesh monster arrived at the mall, still intent on destroying Eleven. After some time, Billy captured Eleven and dragged her to the middle of the food court, where she was to be consumed by the flesh monster. In a last-ditch effort to stop them, the kids started launching fireworks at the creature. Eleven tried to break through to Billy's conscience while the creature was distracted, talking through his memories in an attempt to connect with him. The strategy worked: Billy's long-dormant humanity re-awakened within him.

S3E8 Spider Monster kills Billy2

The Spider Monster kills Billy

S3E8 - Spider Monster10

The creature’s corpse

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.

Following the machine's deactivation, and the gate's closure, the psychic link to the Upside Down was cut off once again, causing the flesh monster to collapse and become inanimate. The creature's corpse fell into the hands of either the American or Russian government, or alternatively, burned up in the "mall-fire" that apparently broke out following the battle's conclusion. The US military arrived to assess the aftermath and stormed the Soviet base; Dr. Owens reached the room containing the Key, and surveyed the smoldering remains of the shut gate.


Vecna's plan

When Vecna emerged as a new threat to Hawkins in 1986, Dustin believed that he was essentially the Mind Flayer's "five-star general". Later, Vecna targeted Nancy Wheeler with the sole purpose of sending Eleven a message. He subjected Nancy to various disturbing visions, including a "giant creature with a gaping mouth" looming over Hawkins.[12]

The Demogorgons in Russia

Meanwhile, Jim Hopper, having been imprisoned in Kamchatka, narrowly escaped the wrath of a Soviet-controlled adult Demogorgon, and was broken out of captivity by Joyce, Murray Bauman and Yuri Ismaylov. After Hopper and his ally Dmitri Antonov were freed, the group discovered a cell containing a piece of the Mind Flayer, which they called 'the particles'. In the same room, the group discovered dozens of juvenile Demogorgons, paralysed and stored in tanks. After the group's exit from the facility, the situation involving the unleashed Demogorgon became more and more chaotic. As Soviet soldiers haphazardly fought the creature, they accidentally shattered the cell holding the captured portion of the Mind Flayer. These released particles immediately entered the bodies of the paralysed Demodogs, reawakening and possessing them, and going on to slaughter the remaining personnel.

Hopper and his allies returned to the base, hoping that destroying the particles in the cell could inflict damage to the Upside Down's hive mind, and therefore assist in the conflict simultaneously occurring in Hawkins. After learning what had happened since their escape, the group started fighting the possessed creatures, still hoping to inflict pain on the hive mind. After chasing Hopper and Joyce around the Soviet base for a lengthy period, the Demogorgons gathered in the same spot, allowing Murray to burn the bulk of them to death with Yuri Ismaylov's flamethrower. The fully grown Demogorgon survived, but moments later, Hopper used a sword to behead the creature. The deaths of the Demogorgons weakened everything else connected to the hive mind: the bats, the vines, and even Vecna himself. By executing the Demogorgons, the group seemed to destroy various fragments of the Mind Flayer, or otherwise rendered its particles unusable.


The Shadow Monster


The Mind Flayer looms above Loch Nora

Mind Flayer inital form

The Mind Flayer's initial form

The Mind Flayer's main form, also known as the "Shadow Monster", is a massive entity, looming at least 50 stories tall.[1] It has a unique body composed entirely of minuscule particles, giving it a misty appearance akin to a shadow.

Originally, the particles took the form of a swirling, storm-like mass, which Henry Creel manipulated and reformed into the Mind Flayer. The Mind Flayer had a vaguely spider-like appearance, due to Henry's love of black widow spiders. The entity has numerous tornado-like limbs, some of which branch into several smaller appendages, and is visually reminiscent of the vines that overrun the Upside Down. The body also features an elongated, flame-shaped head that sprouts from the central body. The creature's presence is often accompanied by unnatural red lightning, which Will describes as a "storm".

Through a telepathic link, Vecna, via the Mind Flayer, could directly control additional entities and beings:

The Particle Fragments

Brimborn fragment

The fragment of the Mind Flayer at Brimborn Steel Works

Pockets of the Mind Flayer’s silver-black mist could move independently while remaining connected to the hive mind and under Vecna’s control.

One of these pockets left the main body and latched itself onto Will Byers, allowing Vecna and the Mind Flayer to possess him. Will's friends and family eventually forced the creature to abandon Will, with the mist fragment flying away to Brimborn Steel Works. When the Mothergate was closed, these particles fell dormant, scattering across the mill's floor. The mist fragment eventually re-awakened when a machine created a new gate in the summer of 1985, renewing the mist fragment's telepathic link. The reanimated particles quickly infected and summoned hordes of rats to the Steel Works, "Flaying" them and melting down their bodies into biomass creatures, which were combined to create a proxy form.

Flayer fragment

The trapped Mind Flayer fragment at Kamchatka

A separate piece of the Mind Flayer was captured by Soviets and stored at a prison camp in Kamchatka; it was presumably extracted via the Soviets' gate to the Upside Down at their base under Starcourt Mall. However, after a captive adult Demogorgon broke free and rampaged the prison, the tank containing the Mind Flayer's particles was shattered in the ensuing gunfire, allowing the particles to possess a number of paralysed Demodogs in tanks. The various Demogorgons then continued to wreak havoc on the base, killing the vast majority of the staff. When Hopper, Joyce and Murray returned to the base, they learned from the dying Warden Melnikov that "the shadow" had escaped and had "entered" the Demogorgons. Later, Murray burned the bulk of the creatures to death with Yuri Ismaylov's flamethrower, with Hopper beheading the adult Demogorgon with a sword. With each creature killed, a piece of the Mind Flayer was also destroyed.

The Spider Monster

Main article: The Spider Monster
St mind flayer

The Mind Flayer's proxy

The Spider Monster, the Mind Flayer's 1985 proxy body, resembled a gargantuan, monstrous spider. This incarnation of the Mind Flayer closely matches its Upside Down counterpart in terms of its shape and proportions. However, unlike the Flayer's main body, the Spider Monster 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 Spider Monster is nigh on indestructible but remains vulnerable to heat.

The Spider Monster is composed of the bodies of the Flayed: dozens of organisms, both human and otherwise, whose bodies were biologically converted to serve the Mind Flayer's will. The Spider Monster was originally relatively small, being composed purely out of Flayed rodent bodies; however, it rapidly grew after finally consuming the converted humans.

The Hospital Monster and the Flesh Thralls

Main article: Hospital Monster & Flesh Thralls

In 1985, the Mind Flayer created an army of smaller entities that served the Spider Monster. They were composed entirely of flesh, cartilage and bone, just like the Spider Monster. The thralls were biological reconsitutions of possessed or "flayed" creatures, including rats and humans. The thralls could merge with one another to form larger monsters.

The most notable of these was the "Hospital Monster", composed of Flayed humans Tom Holloway and Bruce Lowe. Unlike the Spider Monster, the Hospital Monster only vaguely resembled the Shadow Monster, and had a more asymmetrical appearance. The creature was ultimately absorbed into the Spider Monster.

The Shadowy Figure

Shadow Brenner

The entity adopts the form of Brenner

When Henry initially encountered the shadowy entity, the entity first - either literally, or just in Henry's visions - adopted the voice and form of Alice, Virginia and Victor before eventually adopting the persona of Dr. Brenner. The entity claimed it wanted to "study" Henry, and that he was the "most magnificent thing" it had ever encountered. However, the relationship between Henry and "Shadow Brenner" soon grew fractious, with both vying for dominance over the hive mind.[10]


When the Upside Down first emerged as a threat in 1983, it was believed that the Demogorgon was potentially the dimension's sole inhabitant (not including vines), with Nancy Wheeler noting that the creature's hunting patterns were "solitary".[13] However, in 1984, other creatures and entities began to emerge. Dr. Sam Owens and the other scientists at Hawkins Lab observed that all lifeforms native to the Upside Down - including the pack of adolescent Demogorgons which attacked the lab - were linked through a shared hive mind.[14] After Will Byers experienced visions of being attacked by a giant shadowy entity and was later possessed by that same entity, the Party initially concluded that the entity - now nicknamed "the Mind Flayer" after an anatagonist from Dungeons & Dragons - was the force that commanded the Upside Down's hive mind.[5]

From 1984 to 1986, the Party and their allies tended to call the Mind Flayer "him" and "he". They knew little else about the creature, besides 'his' intention to eradicate humanity and merge the human world with the Upside Down; they believed the Mind Flayer was the entity who possessed Billy Hargrove and the Flayed in 1985.

In 1986, Vecna declared himself as the true ruler of the Upside Down to Eleven, explaning how he had refashioned the Mind Flayer entity into its current form upon discovering it in Dimension X, apparently taking control of it (and the hive mind) in the process. After this, Will realized the 'he' who possessed him back in 1984 was actually Vecna, with the Mind Flayer only acting as an extension of his will.[9]

However, despite Vecna claiming supreme control over the hive mind, the relationship and power dynamic between him and the Mind Flayer seemed extremely complex. The dormant cloud of silver-black mist - from which Henry created the Mind Flayer's spider-like "shadow monster" form - was already a living organism.[2][3] Multiple accounts depicted the entity as having a sentience and intelligence all of its own. One of these accounts even suggested that the entity was the source of Henry's powers, with Henry being exposed to its influence when he was accidentally transported to Dimension X as a child. Upon returning home, the sentience forced Henry to murder his family members. Though one account depicted the sentience vanishing after Vecna reformed the mist into the Shadow Monster, it was not necessarily clear if the sentience had been destroyed or defeated. Similarly, even though Henry apparently encountered the entity as a child, Henry did not seem to recognize the entity when re-encountering it as an adult; this could be read as a sign of his "broken memories".[6][10][15]

While a massively powerful being, the Mind Flayer was not without weakness. Most notably, it had a low tolerance to heat, particularly fire. All hosts within its hive mind shared this weakness, resulting in the creature feeling pain whenever a connected entity was exposed to heat, or burned.[16][17]

Powers and abilities

The hive mind

With the Mind Flayer at his side, Vecna's powers greatly expanded. The Mind Flayer's body could split into smaller pieces while sharing a collective consciousness. These smaller pieces could possess other creatures and beings, tying them to the same core consciousness; through the Mind Flayer, Vecna could connect various lifeforms to a shared hive mind, with Vecna's will at the top of the chain. Through the hive mind, a diverse range of beings fell under Vecna's control, including "Demogorgons", Will Byers and the tunnel-organism in 1984, the "Flayed" of 1985, and "Demobats", as well as the roots and vines strewn across the surface of the Upside Down.

Furthermore, through his command of the hive mind, Vecna approached a near-omniscient understanding of his territory. If a Demobat became aware of a trespasser in the Upside Down; Vecna would instantly know. Similarly, if an unlucky visitor were to tread on a vine, Vecna could immediately react and disseminate his will, making the vines spring into action and attack. However, at times, Vecna's connection to his thralls proved to be a glaring vulnerability.


Pieces of the Mind Flayer could only operate when psychically linked to the Upside Down's hive mind (via a gate). However, if the gate closed, the Mind Flayer's particles wouldn't die, unlike the Demogorgons, or the Spider Monster. The particles would instead scatter and turn dormant; if and when a new gate was opened, the particles could immediately reconnect with each other and continue to serve the hive mind's will.

Weather manipulation

The Mind Flayer's presence was almost always accompanied by atmospheric disturbances. In the Upside Down, dark storms would rage in the skies above, with startling red lightning shooting across, illuminating the whole dimension in scarlet light. The storm seemed to be linked to Vecna's emotions; the Mind Flayer was seen looming over Hawkins Middle School, seething with Vecna's anger.

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; her powers would eventually fade completely, and would not be restored until the events of March 1986.

High speed travel

Due to consisting entirely of particles, the Mind Flayer - either in its shadow form, or acting as a fragment - could move incredibly quickly, soaring through the atmosphere at high speed.



Prolonged exposure to high temperature can weaken the Mind Flayer. When Will Byers was exposed to high temperature, it forced the fragment of the Mind Flayer within Will to flee his body. Similarly, when soldiers set the tunnels aflame, the possessed Will writhed in pain.

Dimensional barrier

The dimensional barrier puts hard limits on the Mind Flayer's ability to take over other worlds. However, if the barrier is damaged, the Mind Flayer is able to exert more and more influence in another dimension.

The hive mind

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.


The Mind Flayer had a complex relationship with Henry Creel; it was not necessarily clear which being had a greater influence over the Upside Down and its hive mind.

When Vecna initially re-emerged as a threat to Hawkins in 1986, Dustin believed he was akin to the Mind Flayer's "five-star general". However, when Vecna psychically trapped Eleven within his Mind Lair, Vecna told Eleven that he had been control of the Upside Down the entire time. Vecna explained that he had discovered a dormant version of the Mind Flayer entity upon being trapped in Dimension X, describing it as "the most extraordinary thing of all". Using his psychic powers, Henry gave the Mind Flayer its gigantic, spider-like form and established a psychic connection with the entity, forming a kind of symbiotic relationship. Furthermore, Vecna had apparently been acting through the entity in both 1984 and 1985.

However, according to one account, the relationship between Henry and the entity began much, much earlier, in the 1950s. According to this account, Henry spent much of his childhood living with his family in Rachel, Nevada. One day, Henry explored a nearby cave system while playing with a spyglass. While exploring, Henry stumbled across pieces of scientific equipment stolen from the Nevada Experiment. The equipment unexpectedly activated; Henry and the scientist who stole the equipment were temporarily transported to Dimension X, killing the scientist in the process. In the alternate world, Henry was exposed to the influence of the Mind Flayer entity; from that point on, the entity served as a negative influence on Henry, forcing him to kill various animals and eventually kill his family members.

For reasons unclear, Henry seemed unaware of the entity's influence over him when he spoke in 1979 and 1986, with him describing how he consciously chose to kill his family, and that he had apparently never been to Dimension X before 1979. Though Vecna clearly believed he controlled the hive mind, Dustin's initial assumption that Vecna served as the Mind Flayer's five-star general was possibly accurate after all, even if Vecna himself didn't realise it.

It seemed the Mind Flayer held a deep-seated grudge against Eleven, ever since she closed the Mothergate in 1984. However, the Mind Flayer was later discovered to merely be Vecna's puppet. The entity would likely be totally indifferent towards Eleven, were it not for Vecna's influence.

When Will was trapped in the Upside Down and captured by a Demogorgon, the Mind Flayer became interested in Will and decided to use him for his own purposes, showing no care for him. After Will's rescue, the Mind Flayer started spreading the Upside Down through Hawkins where Will was given visions of the Upside Down. The Mind Flayer eventually confronted Will and started to seek him as a vessel in order to use him to pave into the real world. The Mind Flayer was thwarted two times by Will's friend, Mike, but when Will finally decided to confront the Mind Flayer, he became possessed by a piece of the Mind Flayer. The Mind Flayer slowly took over Will's body and mind, allowing to see and feel everything the Mind Flayer was doing. After Will took advantage of his possession to rescue Jim Hopper where the tunnels were burned by the government soldiers, the Mind Flayer used his possession of Will, forcing him to trick the soldiers into going a trap, as revenge for hurting him through the burning of the tunnels. The Mind Flayer tried to keep his control over Will intact but was stopped by Will's family and Nancy Wheeler as they burned the Mind Flayer out of Will.

A year later, in 1985, despite being freed from the Mind Flayer, he left a huge impact on Will as he could still sense the Mind Flayer's presence whenever he was close. Nevertheless, The Mind Flayer did not seem to remember Will, or harbor any resentment toward him. However, the piece of the Mind Flayer that possessed Will constructed a body for himself out of rats and the Flayed so he could kill Will and his friends as revenge for the events in 1984. However, his plans were thwarted when Joyce Byers closed the Gate, killing the Mind Flayer's proxy body.

In 1986, Will finally discovered the Mind Flayer to be Vecna's puppet and it was him who had possessed him through the Mind Flayer. Will remarked it was bizarre discovering the true culprit behind everything he and his loved ones had been through, but since Vecna had no intentions in giving up in his evil plans, he proposed Vecna had to be killed once and for all.

Upon its return to Earth in 1985, 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. Unlike the rest of the Flayed whom the Mind Flayer had killed to build his proxy body, he kept Billy alive due to his physical strength, and because he was the stepbrother of Max Mayfield, a member of the Party whom Vecna sought to kill as the Party were obstacles in his plans for world domination. 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.


Stranger Things appearances
Season 2 MADMAX Trick or Treat, Freak The Pollywog
Will the Wise Dig Dug The Spy*
The Lost Sister The Mind Flayer The Gate
Season 3 Suzie, Do You Copy? The Mall Rats* The Case of the Missing Lifeguard* The Sauna Test*
The Flayed* E Pluribus Unum* The Bite* The Battle of Starcourt*
Season 4 The Hellfire Club* Vecna's Curse The Monster and the Superhero*
Dear Billy The Nina Project The Dive
The Massacre at Hawkins Lab Papa The Piggyback*
* = The Mind Flayer appears via flashback in "The Spy"
* = The Mind Flayer appears throughout Season 3 as the Spider Monster
* = The Spider Monster appears via flashback in "The Hellfire Club" and "The Monster and the Superhero"
* = The Mind Flayer appears via flashback in "The Piggyback"


The Other Side appearances
Issue 1 Issue 2 Issue 3 Issue 4

Video games

Video game appearances
Dedicated games
Stranger Things: The Game
Stranger Things 3: The Game
Stranger Things: Puzzle Tales
Stranger Things: The VR Experience
Stranger Things VR
Dead by Daylight
The Vanishing

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."[18]

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 the monster was "storm-like", the Graffs began reseraching the look 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.[1]

For Season 4's 'Dimension X' scene, concept artist Michael Maher, Jr. pitched that the Mind Flayer particles were "an anti gravity element" that would lift boulders into the air, "effectively falling upwards". However, the idea was scrapped, as it would have taken too long to explain in the context of the story.[19]


While the entity was called the Shadow Monster throughout Season 2's production, the Duffers decided they had to give it a more formal name. Looking through the Dungeons & Dragons manual, they decided to name the Shadow Monster after the "Mind Flayer", due to their similarities.[20]


  • The Mind Flayer is the second character to be nicknamed after a character from D&D, with the first being the Demogorgon and the third being Vecna.
    • In Dungeons & Dragons, Mind Flayers are a race of psychic, monstrous humanoids with octopus like heads 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".
  • Possessed humans are colder to the touch than average, to the point where the temperature around possessed humans significantly decreases.
  • The scene in which the Shadow Monster infects or enters Will bears resemblance to the possession sequence in 1973's The Exorcist.
  • The 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.
  • Despite having an episode named after it, the Mind Flayer is not physically present in said episode.
  • The Mind Flayer is very similar to the Elder Gods of H.P. Lovecraft, with his work actually tying into the Stranger Things universe, with Lisa from the novel, Darkness on the Edge of Town, being a graduate of the infamous Lovecraftian college "Miskatonic University".


View Gallery For this subject's gallery, see The Mind Flayer/Gallery.

External Links


  1. 1.0 1.1 1.2 1.3 "The Duffer Brothers Recap Stranger Things 2, ‘Chapter Eight: The Mind Flayer’" Vulture. November 8, 2017 - article detailing the show's VFX.
    • The Mind Flayer's height is a point of contention; a later source claimed the creature to be 50 ft tall, rather than 50 stories.
  2. 2.0 2.1 2.2
  3. 3.0 3.1 3.2 The official teleplay for "The Piggyback"
  4. 4.0 4.1 "Stranger Things 4: Ending Explained", from the Netflix Geeked YouTube channel.
  5. 5.0 5.1 "The Mind Flayer"
  6. 6.0 6.1 6.2 Stranger Things: The First Shadow
  7. In SFX Magazine #372, the following is said: "While some of Creel's origin story has been told, [Kate] Trefry emphasises that the version of events seen on screen may not be reliable; we were, she notes, told what happened to the Creel family by Henry himself. '[The First Shadow] is a different perspective,' she says. 'We're reaching back into Henry's past to understand why he is the way he is.'"
  8. @michael_maher_jr on Instagram
  9. 9.0 9.1 "The Piggyback"
  10. 10.0 10.1 10.2 Stranger Things VR
  11. The official teleplay for "Papa"
  12. "Papa"
  13. "The Monster"
  14. "The Spy"
  15. "‘Stranger Things’ Season 4: How the Duffer Brothers Channeled Freddy Krueger for the Vecna Monster" IndieWire. May 31, 2022.
  16. "Dig Dug"
  17. "The Gate"
  18. "Stranger Things 2: Behind the sequel's big, bad 'shadow monster'" Entertainment Weekly. September 28, 2017.
  20. "The Duffer Brothers Recap Stranger Things 2, ‘Chapter Eight: The Mind Flayer’" Vulture. November 8, 2017