Spoilers for Stranger Things Season 2 will follow. While the theory was that Season 2 of Stranger Things would include a Dungeons and Dragons monster called the Thessalhydra, things didn't quite work out that way. The season took its own turn, but in the end, the boys' favorite game did come back into play when the Mindflayer from Dungeons & Dragons was brought in to help study and defeat the big Season 2 bad, aka the Shadow Monster. But while the name is super visceral sounding, "mindflayer" doesn't exactly tell non D&D experts the whole story.
In the series, Dustin looks for clues about the group's new foe in his D&D manual and in a moment straight out of the high school seasons of Buffy the Vampire Slayer (trust me on this one), he finds a monster that kinda resembles the one they're facing in Hawkins. It's enough information to form a plan to defeat the creature taking over his buddy Will's brain (seriously, that kid can't catch a break), and maybe even save Hawkins.
The Shadow Monster, it appears, is controlling various beings in and around Hawkins via something between a virus and possession. It's got its smoky hooks into the demo-dogs (baby demogorgons, one of whom is a former pet of Dustin's), the creepy and seemingly sentient vines underneath the town, and poor Will. And, as it turns out, the Mindflayer is actually a very accurate stand-in for the problem that Dustin & Co. were trying desperately to solve.
Mindflayers, or illithids, are powerful overlords who have been known to take over entire empires — sort of like the mini one the Shadow Monster was attempting to unleash in Stranger Things Season 2. And while the kiddos were able to shake him this season, the official D&D description should certainly make fans feel uneasy about the fate of Hawkins in Season 3:
"In eons past, illithids controlled empires that spanned the planes. They subjugated and consequently warped whole races of humanoid slaves, including the githyanki and githzerai, the grimlocks, and the kuo-toa. Conjoined by a collective consciousness, the illithids hatch plots as far-reaching and evil as their fathomless minds can conceive."
Ignoring the names of creatures you probably don't recognize if you're not into the game itself, let's focus on phrases like "warped whole races of humanoid slaves." If that doesn't describe Will and even the demo-dogs when the Shadow Monster has them in his grips and made them do their bidding, I don't know what does. (Jury is still out on whether D&D Mindflayers can keep the kids they possess from using Morse Code to communicate with their enemies like Will did, though.)
Of course, when it comes to appearance, the Mindflayer looks, well, pretty menacing. I'm not sure what most people would assume a flayer of minds looks like, but according to the D&D realm, it looks a lot like Bill Nighy's Davy Jones from the many Pirates of the Caribbean movies. Just look for yourself: these things are basically squid-face humanoids.
Apparently, among D&D gamers, there is even such a thing as a cute Mindflayer. (I would say I'm surprised, but fandom is a powerful thing that makes just about anything cute if you try hard enough.) Fans have created everything from fan art of young, cutesy mindflayers to comics that joke about the seemingly terrifying creatures.
Of course, none of these iterations look nothing like the giant spider slash praying mantis made of smoke that takes over Hawkins, but hey, Dustin never said it was an exact match. And at the end of the day, Hawkins was saved. We can probably let the small details go, OK?