During the seasons of Stranger Things we can see that the Mind Flayer can join a human and has power over the host.

Will was the first one to suffer this but they could take it out before the portal was closed by Eleven.

Does the Mind Flayer that was inside Will return back to the Upside Down world or it stays in Hawkings?

Because in the 3rd season, Will tries to explain to the rest of the group that maybe he didn't return to his world. And at the start of the last season we can see that when the Russians were trying to open it and some "tentacles" or something similar were emerging.


1 Answer 1


According to Will in the season 3 episode, The Sauna Test, it appears while most of the Mind Flayer may still exist in the Upside Down and is probably running the show from there, another part of it still existed in Hawkins, as it (or at least, this part of it) was seeking to become more corporeal during the course of season 3.

3.04 Transcript:

WILL: I didn't think it was anything at first. I mean, I think I just didn't want to believe it. The first time I felt it was at Day of the Dead.

MIKE: Power went out that night, too.-

WILL: And then I felt it again at the field near the Nelson farm the next day. Then again yesterday outside Castle Byers.

MAX: What does it feel like?

WILL: It's almost like You know when you drop on a roller coaster? -

MIKE: Sure.

MAX: Yeah.


WILL: It's like everything inside your body is just sinking all at once, but this is worse. Your body it goes cold and and you can't breathe. I've felt it before, whenever he was close.

MAX: Whenever who was close?

WILL: The Mind Flayer.

Eleven: I closed the gate.

WILL: I know, but what if he never left? What if we locked him out here with us? This is him. All of him. But, that day on the field, a part of him attached itself to me. My mom got it out of me and Eleven closed the gate. But the part that was still in me, what if it's still in our world? In Hawkins.

MAX: I don't understand.The Demodogs died when El closed the gate. If the brain dies, the body dies.

WILL: We can't take any chances. We need to assume the worst. The Mind Flayer's back. Yeah. And if he is, he'd want to attach himself to someone again. A new me.

LUCAS: A new host.

ELEVEN: How can you tell if someone is a host?

In addition there is even a brief conversation from the kids in another scene about "mixing chemicals" in order to make "a new substance" to explain away why the victims were eating certain things, but in all honesty, there isn't enough information to necessarily understand the Mind Flayer's full plan with the chemical-eating subplot.

  • 2
    Adding to this I also imagine it to be like a hive mind and so long as the gate is partially open it can control parts of it from the Upside Down, like the Demogorgon and the flayed and the bit that attached itself to Will.
    – moonCat93
    Commented Aug 23, 2019 at 14:38
  • The Mind flayer never left the upside down. It’s still there running the show, the monster it created was a simple avatar to attempt to kill El. El is its only enemy powerful enough to close the gate once it was fully open. It’s plan was to kill her first before attempting anything else. Commented Aug 23, 2019 at 16:03
  • @morbo, while that is probably true (& yes, 2 the MF's bigger plans), I don't recall any dialogue/scenes confirming anything more substantial about the way the MF "technically" works. I think Will's explanation that "part of it" was in H is accurate, despite contemplating notions of astral projection, corporeal-materialization, quantum entanglement btw dimensions, & it having 'bee-hive mind" that can telecommunication with other parts of itself seems mostly self-evident. I did readjust my A to be more specific. Commented Aug 23, 2019 at 16:55

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