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 inhabiting the Upside Down. It was introduced in Stranger Things's second season, and is considered one of the show's main antagonists.



The history of the Mind Flayer prior to October 1984 remains a mystery. Exactly how long it had existed for, and how and why it came into existence, is unknown.


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.


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.

As time passed, Will's connection with the Mind Flayer deepened more, 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 he was afraid and exploited their connection to use him to massacre the scientists at the Hawkins Lab.

The huge silhouette of the Mind Flayer later appeared behind the Gate as Eleven attempted to close it. The Mind Flayer attempted to stop El, sending one of its coils through the Gate to attack her as well as commanding his minions to swarm both her and Hopper; however, El successfully disintegrated much of the coil. She then channeled her anger to overpower the Mind Flayer and finished the job of closing the Gate, sealing it back inside the Upside Down.

Sometime later, during the Hawkins Middle School Snow Ball, the Mind Flayer loomed over the Upside Down version of the school, having survived the assault on the Gate.


The Mind Flayer is gargantuan and spider-like, being at least 50 stories tall. The precise details of its anatomy remain unknown, due to the thick, black cloud-like substance which envelops it. It is unclear whether it is entirely composed of this substance, or if its body contains any solid elements.

However, the creature does appear to have multiple limbs, some of which branch into several appendages; these limbs visually resemble the tendrils and vines present in the Upside Down. It seems to have an elongated, almost match flame shaped head which sprouts from the central body. Its presence is often accompanied by dramatic red lightning, which is mentioned frequently by Will as "The Storm".

Pockets of the 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 flying away into the sky.


The Mind Flayer telepathically commands its army, consisting of Demodogs and the tendrils, to kill and destroy humans (except for its host Will). It also displays a sense of human-level intelligence, as it forced Will to lie in order to kill numerous soldiers.


  • 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, it sent multiple Demodogs to the tunnels in order to deal with the problem. It 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 it 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 his restraints and throttle Joyce effortlessly with one hand while she attempted to free Will from the creature's possession.
  • Tempestakinesis: The creature could manipulate its own storm/cloud-like body to forcibly possess and attack. It was able to possess Will through an episode he was suffering, despite its physical body remaining in the Upside Down. Through the Gate, it also attempted to attack Eleven as she closed it, but her great psychic power was able to block its attempt. In addition, the creature was often surrounded by red electrical storms. While the nature of these storms is not entirely clear, it is possible the Mind Flayer was responsible for their creation.

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."[1]

MindFlayer Conceptart1

Concept art of the Mind Flayer confronting Will.

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.[2]


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.[3]


  • 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 his 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.
  • 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.  More recent editions have referred to Mind Flayers as "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.


View Gallery

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


  1. 1.0 1.1 "Stranger Things 2: Behind the sequel's big, bad 'shadow monster'" Entertainment Weekly. September 28, 2017.
  2. "How Stranger Things 2 Transformed Hawkins Into the Upside Down" Vulture. November 8, 2017.
  3. "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 systemVines
Visitors Joyce ByersWill ByersElevenSteve HarringtonDustin HendersonBarbara HollandJim HopperMax MayfieldBob NewbyShepardLucas SinclairMike WheelerNancy Wheeler
Miscellaneous Upside Down eggThe Upside Down (episode)Dungeons & DragonsThe Void
Articles may contain spoilers.