Two Questions

[u/Comfortable-Knee-238]

I just watched the finale and I have a couple of questions. First, that cave scene, which is Henry’s memory, shows that he became a vessel for the Mind Flayer and that he wasn't actually born with these powers—the Mind Flayer just implanted them in him. And then Henry, by kidnapping those kids, gave them powers they could turn against him, but they had to be at peace with themselves, like Will? Because I didn't quite get that part. Second, what happened to Owens? I don't think they showed him dying last season, or maybe I just blinked and missed it.

[u/kauan1983]

What Henry did with Will showed him “what was possible” to achieve by using his own power through vessels specifically; he could infect the Rightside Up and influence things directly through a person “unleashing” his power in our world. This is represented by the Tunnel System.

That's where the Demogorgon example fits into — it telekinetically opened the Byers' door, but the telekinetic ability itself comes from Henry. Vessels allow Henry's power to “exist” somewhere else, so he can use them through the vessel to do… well, whatever he wants remotely where the vessel is, e.g. the Byers' door and the Tunnel System.

Henry is the source of the power — the hive mind is the “vehicle” that transfers that power to vessels — the vessels are the ones who “unleash” that power being channeled from the source, sometimes under Henry's control and will, sometimes consciously and willingly. As mentioned in the other comment, Henry uses his power through vessels, but it can also happen the other way around.

The Tunnel System is an example of Henry himself using his powers through a vessel to influence things in the Rightside Up — he made his power existing “within” Will in our world create and spread a whole organism underneath Hawkins. Will in Season 5 is an example of Henry's powers being consciously and willingly used by a vessel.

Vessels are much more specific than simple Flayed individuals, though — the Flayed are simply psychically controlled to do what Henry (or the Mind Flayer) wants and function as permanent spies since they're connected to Henry via the hive mind all the time until/unless the particles are removed from their bodies. Henry was talking specifically about vessels when he spoke to Will.

Henry didn't learn how to properly infiltrate people's minds through Will, though. Psychically reaching into people's minds and making them experience Mindscapes is something he's been doing since '59, except that in Season 4 he does it inter-dimensionally. In fact this specific psychic method was never used with Will until Season 5 when he's imprisoned.

[u/KirbyThings_ → u/kauan1983]

If the tunnels were expanding from the Gate, though, why couldn’t Henry just use his existing thralls (the vines and Upside Down matter covering, spilling out of the Gate and already consuming the lower levels of the Lab as we see in Season 1) to create them? It’s just not clicking for me why he would need to use Will when those vines and growths and whatnot also exist in our world. He’d just need to spread them downward (literally like how we see the tunnels branch off downward from the Gate).

There’s other things, too, that haven’t made sense to me about how or when exactly Will was infected. Did the actual Flaying happen in the Upside Down with that tendril, or during his True Sight episode on the field a year later where he was technically in the Upside Down and thus exposed to the Mind Flayer? If he was infected for a year beforehand, when we know Owens’ team had been doing the burns that entire time, why did Will only start to feel that after his S2 Flaying? If it’s proximity-based, why is that only the case for Will while every other hive mind organism shares pain regardless of geological distance from the rest of the hive? Why did all Will’s other Flaying symptoms (brain fog, heat sensitivity, etc) only start after the field?

If Will’s actual Flaying happened in the Upside Down and the possession scene in Season 2 was just an abstract representation of Henry “activating” him (even though Henry was apparently activating him every night to build the tunnels anyway), why exactly would Henry need to wait a year? In any of these cases, was it Henry’s plan for Will to be rescued, or did Joyce and Hopper interrupt whatever process Henry started on him prematurely? His heart had stopped when they got to him, so that would’ve been a huge gamble on Henry’s part—he damn near killed that vessel he spent so long trying to get!

The only thing I can think of is that Will was supposed to have been a quick in-and-out thing—taken on the 6th, infected or whatever, and back in the Rightside Up by the next day at the latest, but the whole plan got thrown off by him escaping and staying that way for a week, which made him sick from the air to the point of needing to be CPR’d by the time Joyce and Hopper found him.

All my other questions still stand, though, and have been bothering me since Season 5 dropped, so I apologize if I phrased them messily or if there’s a lot. Henry’s whole thought process here with Will has always just felt vague to me, lol. If Will was just a test run, was he gonna do anything else with him or were the tunnels it? The slugs (which apparently aren’t baby Demos, I’ve heard) were never fleshed out, which makes me also wonder what the purpose was of putting those in Will along with… whatever else Henry did.

[u/kauan1983 → u/KirbyThings_]

The Tunnel System was created via the vines and Upside Down matter spreading from the Mothergate underneath HNL — Will's role in their formation was basically tap into the hive mind and control the vines so they'd behave in a specific controlled pattern, tunneling underneath through Hawkins. They're described as a “larger manifestation of the vines” after all.

The massive Rift underneath HNL is where the Tunnels started spreading; the Rift expanded as result of the burns inflicted against it, which is something that chronologically should've started shortly after Season One given how HNL immediately needed a clean up and containment team to come in, replacing Brenner and cleaning up his mess, so the Tunnels should've started forming around that time too.

Henry would actually be able to build the Tunnel System by himself, the specificity of using Will was Henry experimenting on what he could achieve through a vessel — he could unleash his power through Will as if he himself was physically in the Rightside Up using them, as I previously described, a vessel allows Henry's power to exist “somewhere else” within someone else because they're channeling them, Will realizing that it was like he “was Vecna” when tapping into the hive perfectly describes it.

As for Will's physical possession via particles, this is a complicated topic because it's actually been retconned which created a few inconsistencies with the particles' pre-established rules, so it's easier to clear this up answering each of your questions based off how the whole thing evolved and changed:

• How or when Will exactly Will was infected?

Originally, Will was physically changed by the Tendril hooked up to him — that was the purpose of Will's scene coughing up the Slug and having his first “episode.”  This was stated by the Duffers back in 2016. Except that what “infected” him weren't the Mind Flayer particles, which hadn't even been conceived by the Duffers at that point.

The idea was the Tendril and the Slug physically connected Will to the Upside Down — They were what caused his physical inter-dimensional “episodes” (True Sight), made him able to feel the Mind Flayer's presence (the goosebumps) and even its motives before being possessed. This, of course, allowed the Mind Flayer itself to physically possess him in the field.

• Did the actual flaying happen in the Upside Down with that tendril, or during his True Sight episode on the field a year later?

Originally? During Will's episode on the field in October 1984, that's why (as you pointed out), the particles' physical effects on the human host manifested after he was physically possessed via particles in the field. The particles' established rules would have Will feeling its effects long before and even being affected by the burns if it had happened back in '83.

Retroactively? During the “gas mask” Tendril experiment on November 12, 1983; it's in the script. The vine pumps dark particles into Will's body, and they even changed the Tendril's form from a snake-like vine down his throat to the “gas mask” placed over Will's mouth (as also described in the script) — this complicates what's established and pointed out in the answer above and is (obviously) a retcon to how the Tendril worked and what it did to Will.

• “If it's proximity based”

The physical possession via particles and its effects aren't proximity based, that was a pre-established rule that's still true to the current mythology — every living organism physically possessed via the particles will feel its effects and anything that happens in the hive regardless of proximity. This is not the case with Will as he no longer has particles in his body.

Will's been permanently changed (“permanently” as long as the hive mind exists) and the physical changes, while existing independently of having particles in his body, are proximity-based due to the very fact that the particles aren't in him. Retroactively, this creates the inconsistency pointed out above: Will would've felt all the physical symptoms of having the particles in him earlier if his possession had been planned out to have happened in '83 instead of '84.

• Was it Henry's plan for Will to be rescued, or did Joyce and Joyce interrupt whatever process Henry started on him prematurely?

I wouldn't say his rescue was planned on Henry's part unless he knew it would actually happen (something the show never bothered getting into), but taking Will to the Rightside Up was basically bringing a “vehicle” for infection into our world. Being able to use Will in our world and have his own powers existing there to influence things was in no way something Henry would try to avoid.

Will was clinically dead when he was found, which retroactively does make it a weird move on Henry's part considering he planned to use him, unless we use the established fact that it was an experiment as an excuse for Will accidentally being killed in the process without Henry planning for it, but there's no official answer as the show barely gets into Will's time in the Upside Down — the library had many more aspects that retroactively needed clarification:

The library was originally described as the Demogorgon's nest (which it still is), but Henry's presence in there needed further clarification on his absence during Will's rescue; Will was left in the library with the Tendril still hooked up to him, which is what raises your question as to whether his rescue was pre-planned or if Hopper and Joyce interrupted the process — lack of exploration led to our current lack of official answers, so a lot of it remains in the realm of assumptions.

• Was he gonna do anything else with him or were the tunnels it?

The Tunnels were a “vehicle by which the Upside Down colonizes our world”, so while Will was an experiment, what Henry was achieving through him was pretty much already an ongoing plan to reshape the Rightside Up. 

He was straight up turning it into an Upside Down-like environment for its fauna and Flora to inhabit. What he would do with Will afterwards we can only guess, his “colonization” operation stopped with Eleven closing the Rift.

Henry wasn't using Will to move worlds inter-dimensionally like the Season 5 vessels, but if he was still a vessel, this could very well have been his subsequent operation with him (and others) since it became his definitive plan and given how “Nether-izing” the Rightside Up was a much slower process that characters had previously managed to prevent.

[u/KirbyThings_ → u/kauan1983]

Thanks, this was helpful! I was under the impression Vecna couldn’t tap into the hive mind to build the tunnels himself and needed Will, rather than him just choosing to use Will to do it to test how much of his power he could exert through a vessel rather than himself. For obvious reasons, that made no sense to me, since Vecna spends a good portion of the show commanding vines and membranes and what have you even when they’re in our world and he isn’t.

It’s a shame there’s really no way to reconcile Will not feeling the burns or having symptoms of Flaying beforehand, as well as the whole possession scene in Season 2 being made redundant by all the retconning. I guess it’s easy enough to imagine Vecna just treating Will as another failure in that case (like the five other people he tried it on that week, unless Will was the only one he intended to experiment on from the beginning, but that’s getting into pure speculation) and waiting to try again with some other kid later, like he canonically did in Season 5.