WARNING: This article contains spoilers for the second season of Stranger Things, streaming now on Netflix.


When viewers got their first look at Stranger Things' second season, what stood out most was the eerily Lovecraftian entity looming over Hawkins, Indiana. Of course, the red sky and lightning made it all the more ominous, exciting fans eager to see how the Duffer Brothers would upstage the Demogorgon. Many speculated the monster was the Thessalhydra from Dungeons & Dragons, foreshadowed by the game played in the closing scenes of the Season 1 finale.

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That D&D monster was an acid-spewing, eight-headed hydra, with each of those heads centered around a mouth containing jagged teeth. It also had a tail equipped with pincers to grab victims and feed into its mouth, but by design alone, it bore no resemblance to what we witnessed in the trailers, which was a towering multi-limbed creature that looked like a giant spider. Will Byers (Noah Schnapp), who spent much of the first season as a prisoner of the Upside Down, was the only one who could see the entity, which he called the Shadow Monster because its body consisted of, well, shadow and smoke.

However, as Season 2 neared its climax, Dustin Henderson (Gaten Matarazzo) dived into the Dungeons & Dragons Monsters Manual to rebrand it as the Mind Flayer because, unlike the Thessalhydra's physical approach to killing its enemies, this creature was more cerebral and focused on mental attacks. That said, to dissect exactly what this was that tormented Will and Hawkins, we have to go a few layers deeper, because by the time Season 2 wrapped, we'd come to discover it was so much more than a monster.

A Biological Beast

The Shadow Monster was a sentient being with an intelligence that could control creatures from the Upside Down. When Will returned from that dark mirror universe at the end of Season 1, he coughed up slugs and was plagued by visions of the destruction he Shadow Monster wanted to inflict. Dr. Sam Owens (Paul Reiser), who took over from Dr. Brenner (Matthew Modine) as head of Hawkins National Laboratory, oversaw Will's recovery, and his diagnosis played a big part in determining what this thing truly was.

Owens revealed that after returning from the Upside Down, Will wasn't just connected to it, he was infected by it. The doctor also divulged to Will's mom, Joyce (Winona Ryder), and Chief Jim Hopper (David Harbour) that this virus was quickly spreading through the boy's mind and body, confirmed through a series of brain scans. The multiple seizures Will suffered throughout the season was a side effect of the virus as it transported him to and from the Upside Down. That was happening because the Shadow Monster was trying to catch him in that dark dimension in order to prepare him as a vessel for something much more sinister, and also to make the infection permanent.

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A Demonic Parasite

That's right, the Shadow Monster wasn't only determined to infect Will, it wanted to possess him. After Joyce's new boyfriend, Bob Newby (Sam Astin), offered Will advice on how to confront nightmares, the boy tried to do so against the Shadow Monster. However, he fell into its trap as the Shadow Monster assimilated him, becoming part of Will in the real world. It began to take control of his mind, using him as a conduit to spy on the townsfolk who were trying to stop it. That resulted in an "evil Will," and culminated with the boy tricking soldiers into a trap, where they became easy prey for Demodogs.

Mike Wheeler (Finn Wolfhard) discovered the subterfuge, and the group sequestered Will in a location unknown to him so he couldn't transmit information to the Shadow Monster. But what Joyce, his brother Jonathan (Charlie Heaton) and Mike's sister Nancy Wheeler (Natalia Dyer) really planned was a quarantine that would act as a science-based exorcism. The Shadow Monster required a cold environment, similar to that of the bleak Upside Down, so as long as it was in Will's body it couldn't tolerate heat. Joyce realized that after "evil Will" insisted on a cold bath -- "He likes it cold," he chillingly told his mom early in the season -- so she used electric heaters, subjecting her son to intense heat in the hopes he'd sweat out the monster like a fever. It worked, and and the created was purged back to the Upside Down.

A Hive-Mind

In a strategy session about how to defeat the Shadow Monster, Dustin realized that due to its psionic powers and apparent hive-mind capabilities, the creature had the characteristics of the Mind Flayer from D&D. Basically, that meant it was the Brainiac of the Upside Down, as demonstrated when it controlled the Demodogs. When those canine-like creatures attacked Steve (Joe Keery), Dustin, Lucas and new girl Max (Sadie Sink) at the junkyard, they broke off the hunt and left as pack when the Mind Flayer summoned them through "evil Will," setting the trap for the soldiers at Hawkins National Laboratory, who had earlier burned off vines winding through the tunnels beneath the town.

Why are those vines important to the entity? Well, while Will was a mental extension of the Mind Flayer, these vines were a physical extension, growing out from the rift at the lab. When Eleven was sealed that gate into the Upside Down, she also forced the Mind Flayer back because it had left Will's body and was trying to reenter the real world. However, she closed the rift with the creature inside, and cut off its connection to the Demodogs, killing them in the process and rendering the underground network dead.

So in essence, while this entity wasn't a hydra, it clearly had several heads or, in this case, means of attacking the residents of Hawkins. It remains to be seen what new measures will be deployed by the creature to seek revenge, because as the final shot of Season 2 indicates, the Mind Flayer is poised to strike again.


Now streaming on Netflix, the second season of Stranger Things stars Winona Ryder, David Harbour, Finn Wolfhard, Millie Bobby Brown, Gaten Matarazzo, Caleb McLaughlin, Natalia Dyer, Charlie Heaton, Cara Buono, Matthew Modine, Noah Schnapp, Joe Keery, Sadie Sink and Dacre Montgomery.