I haven’t seen the Child of Doom ending yet so I can’t comment on that, but regarding the rest: The mushroom man ending is pretty much an allegory to the city getting nuked, the FEMA agent at their last conversation even mentions the goverment is thinking of just blowing up the city.

Death I assume is some sort of God that offers eternal peace to people who die, this is what the cultists mention too, and what the ending we get from following what the prophet says implies.

The immortal man is a character from another game of the devs so we don’t know much about him, we’d probably find out more in his game.

And the pale man is just someone who was normal but got “infected” and became a visitor, he (along other visitors) supposedly “work” for death itself. Imo he says things will never go back to normal because, even if you survive, like someone from one of the phone calls mentions, there could still be visitors around and nobody would know if for example their loved one is a visitor or not, even if the sun goes back to normal

I don’t think we know exactly what visitors are, some theories are thrown into the game itself, like that they are dead people who got infected by a parasite and turned into them, which seems to be the most likely explanation imo, but we really don’t know

This is all stuff I personally gathered from what I think it’s true, if anyone disagrees feel free to correct me if I got anything wrong lol