I have a theory.

If they aren't useful for the Entity they are probably incapable of living anyway.

^

The Void is where they go after they've lost all hope. They quite literally have no hope to carry on and continue trying to live and survive so there they exist in torment, husks of their former selves, completely devoid of all hope and likely all other emotions.

It's quite possible that returning survivors to their original homes would also alert the people of those world's to the Entity's existence, and therefore pose as a potential threat / create complications. So there's also that, also just generally speaking...

Why the hell would an Evil Primordial Deity feeding off the hope of its victims let them go??? Even if they were useless to the entity, why let them go? Like what, the Entity all of a sudden feels nice and charitable maybe even a little guilty after a torment of 100 years?

Which by the way, it's suggested or at least implied that Entity is extremely goddamn old, according to the wiki:

"The rich presence of auric particles and cells also indicates that The Entity is far more ancient than the Observer and his people ever suspected, leading to his speculation that The Entity is an "Original One", an "Ancient"

So we're talking like, origin of the universe old, an existence as infinite as time which we as humans can hardly comprehend. That's part of the whole mystery of it all, the point I'm getting at here is, 100 years might be a whole lifetime for us, it could be an ungodly long amount of time to be in torture and suffering, but in the grand scheme of the universe 100 years may as well be equated to a second. Potentially less than. So, even if the entity did let anyone go, it certainly would not be after such an insignificant period of 100 or even 500 years. Again, let alone at all, the entity definitely doesn't let anyone escape no one that we know of has ever been known to escape. Not benedict, not vigo, not the observer, nobody.

Hey Apple.

Well supposedly the journal was talking about the serum, which is what our alchemist used to escape the void. I doubt Vigo used the serum to escape the void and just used the auric particles in the fog to manifest an escape for himself.

Remember that Talbot started experimenting with the serum, because he found the notes of Vigo about it, so I think the serum was still used in some way to allow Vigo to escape the Void, perhaps it helped manipulate the realm, like we know that he can do, but while Talbot used the serum in the wrong way and needed to make a deal to escape, Vigo did it on his own.

I think it's generally thought of the other way around. A year in the realm of the entity might be a second in the real world, this wa

That way the torment the survivors suffer through seems so much longer and dragged on, never ending as seconds blur as years and minutes are near centuries, making it all the more mentally more draining and cruel. It adds a mental element to the torment survivors go through and requires more enduring perseverance and hope on the part of a survivor to survive.

But I mean yeah, the principle of Time being super wonky and non-linear is something we all agree on about the story.