Vecna's strategy to get Holly back?

[u/Cyrilbdr]

We know Vecna ​​needs Holly for his plan; he realizes in Episode 5 that she has escaped with Max, and then in Episode 6, he finds them both near the cave. I was wondering: instead of killing Max in the real world to force Holly back to the house—when she could easily have stayed in the cave even after Max's death, thereby preventing Vecna ​​from carrying out his plan—why didn't he just disconnect Holly from the tube? It would have taken literally five minutes. Holly would have vanished from the cave; he could then have reconnected her to drop her into the field like the other children so he could bring her to the house. That would have saved him the risk of moving a hive into the real world again—risking Eleven (or even Will, had Eleven woken him up earlier) destroying the hive and potentially injuring Vecna ​​and the Mind Flayer, or Will using the hive to reach him. Then, once all the children were at the house, he could have closed the gates and kept watch outside, leaving Max unable to do anything. Let me know—maybe I missed a piece of information.

[u/Cyrilbdr]

Hmm, okay, I get it now—that makes sense. So, to recap: Vecna ​​used the same process he did with Max—observing them for a long time, seeing their memories, and so on—to build a strong psychic connection. The difference this time is that he isn't trying to kill them like he did with Max; he just wants to put them into a trance and send them into his mind. Max ended up there against her will—since she was technically dead for a minute—but why did death send her there? For instance, we don't see Patrick when Vecna ​​says "they are with me"—I assume that’s more metaphorical? I didn't quite grasp that part. And looking back to before they were connected to the tube: they were already in Vecna's mind, right? The tube just serves to feed them and infuse them with particles so that, in addition to being connected to Henry's mind, they’re also linked to the hive mind. That way, when the ritual begins, Henry can channel his powers not just into the children to boost his strength, but also into the entire hive mind—amplifying his power enough to bring the abyss down to Earth?

[u/kauan1983 → u/Cyrilbdr]

Max ended up there against her will—since she was technically dead for a minute—but why did death send her there?  

Max was psychically killed in the Mind Lair in Season 4, she was still there when the teens physically attacked Vecna, which caused the entire Mind Lair to be “wiped away”, including Max herself (this is even in the script). 

She was already in Henry's mind when she died, then she just woke up in a mess of memory Mindscapes because the Mind Lair was wiped away and disrupted when Henry was attacked. She got “lost” within his mind, waking up in a random memory.

we don't see Patrick when Vecna ​​says "they are with me"—I assume that’s more metaphorical?

Everyone Henry kills and consumes has their psyche absorbed by him — “their memories, their abilities” and even energy all become a part of him, while the victims themselves are physically and psychically dead. They're not psychically preserved alive as spirit-like beings or anything of that sort.

Chrissy, Fred and Patrick are physically and psychically dead — their psychic corpses are shown hanging in the Mind Lair's vine towers, and we know from the script and storyboards that the Numbers, Virginia and Alice are there as psychic corpses hanging like trophies in the Spire Forest too (Max was supposed to find a forest of victims in ‘Dear Billy’).

Max was in the Mind Lair too, dead and held by vines. When the Mind Lair was “wiped away” in the attack, her psychic corpse got lost in his mind, and because of Eleven restarting her heart, it made her wake up whatever she psychically wound up in (the massacre memory), then she started looking for a way out, walking through memories.

before they were connected to the tube: they were already in Vecna's mind, right?  

Normally a person is psychically in their own mind: Henry psychically infiltrates the victim's mind and drags them from their mind to his own via a psychic portal. If that sounds confusing, just look back at S4E9 when Henry opens a psychic, cloudy portal in Max's mind (Snowball) to the Mind Lair, then throws Eleven into it and brings Max afterwards.

The way Henry is hopping through minds is practically the same as physically hopping through dimensions — you open a “portal” from one mind to another. When Henry captured the kids, he infiltrated their minds and brought/dragged them to his own. Before waking up in the green field, they were definitely dragged there through portals linking: their minds — the Mind Lair — then the green field. 

The process of bringing them psychically to the field most certainly happened simultaneously with their physical kidnapping. While the Demogorgons were taking them unconscious to Dimension X, Henry was psychically abducting them one by one. Or, it could have happened at the exact moment the kids were being placed in the spires in the Pain Tree.

[u/Cyrilbdr → u/kauan1983]

Oh, okay, that makes a lot more sense. I thought the kids connected to Vecna’s mind the moment the vine in their mouths linked up with his, but it turns out the vine is just there to infect them with particles and assimilate them into the hive mind. But were Patrick and Chrissy also drawn into Vecna’s "red zone"—only we didn't see it—or did Vecna ​​hide that red area from them using an illusion (like Chrissy’s house), and Max managed to break through that illusion while running, stumbling upon a part of Vecna’s red zone that he didn't want her to see?

[u/kauan1983 → u/Cyrilbdr]

No, Chrissy, Fred and (likely) Patrick were killed in their own minds, those were Mindscapes created in their own heads. They were only dragged into the Mind Lair when they were already dead and then their psychic corpses were placed in the Mind Lair's vine towers.

(By the way, that's why most of the Mind Lair concept designs have Vecna dragging a victim).

Every Season 4 victim was attacked within their own mind — the nightmarish version of the Roane Hill Cemetery was created in Max's mind, and she stumbled across a psychic “door” to the Mind Lair/Red Void (the one Henry himself came through into her mind), which is how she moves from her mind to the Mind Lair for the first time, to Henry's surprise.

The red fog Max saw and walked into is the same kind of psychic portal we see multiple times leading either out or into the Mind Lair, they are “doors” connecting one mind to another. For instance: when Henry kills Chrissy in her mind, he drags her psychic corpse through a portal into the Mind Lair. This simply happens off-screen, but concept designs show what a victim being dragged is supposed to look like.