Ok, ended up doing some more detarune analysis and came to a conclusion I don't know what to do with, not as much images this time, though hopefully this works:
One of the less discussed aspects of this game's deeplore is the "other side of the lake". Its an area that has only recently become relevant as of the chapter 5 weird route, in which Noelle attempts to cross the lake using our commands as the Soul to break through the boundaries of hometown's map. Where this is going is for know unknown, but there are two camps:
The first and most popular is the bottom of the lake: The idea that the Depths, a route to the Shelter or some other mass of darkness is below the lake has been popular for some time, and the Weird route having us go down into it is promising. That being said: very little supports this, namely:
Noelle at the start of this sequence "(that if I stayed by your side any longer, you were going to drag me down with you. Drag me down somewhere no one is supposed to go.)". While metaphorical this parallel's the walk, as both Kris and Noelle walk deeper into the lake.
Jackenstein Fight: The Tutu attack has a backdrop of a series of underground chambers connected to a riverbed.
Susie's stone falling, though this seems more important to the other option
The other option is a location on the opposite side of Hometowns lake: And there's a LOT to imply this:
Noelle explicitly refers to wanting to see the other side of the lake, which is what she wants to use the Soul's power for: "If you tell me to, I can do things that are impossible... The other side of the lake. We always wanted to see what was there... Kris, let's go there."
In Man country, one of the aces finds a place at the edge of the world after "TRYING TO SEE AS FAR AS I CAN". The idea of seeing too far is a also alluded to by Spamton in his monologue at the end of his weird route fight. "YOU LOST IT WHEN YOU TRIED TO SEE TOO FAR.... YOU LOST IT...". The area also references breadcrumb glitch, a Mother 1 glitch only otherwise referenced before the Weird Route Lake Scene.
When Susie's lake skip fails, she says "We'll see how far YOU get at the lake next time." The next time either of them are at the lake on either route is at the end of the festival, where the lake scene happens. Susie may not be able to get us there, but someone else can.
The Mantle Game sees us cross a body of water to progress in board 2, one we should usually be bared from besides a glimpse. The other side of the lake remains only a glimpse for characters.
This "other side" is to me the most promising, though it begs the question. What is on the other side of the lake? This is difficult, because not even the characters seem to actually know what's there, but I've tried to document everything that seems to relate to this. Here is everything we know:
1. It is cold:
Noelle comments on the water getting colder as she progresses, from "the water's nice" to "its colder than I thought."
The ocean in Board 2 goes from tropical islands to snowy wastelands as we go further north. Like with the lake, the further you go towards the other side, the colder it becomes.
In the Smile Survey, the phrase "The Place where it Snowed" is the only comment that gets the response "You know that isn't until later.". This seems to parallel Hometown as the "Place where it Rained", which leads into.
2. It has buildings and evidence of a town/city:
"The place where it snowed" immediately compares this place with a town.
One of Noelle's backgrounds on her computer (I think) is "a picture of a far-off, snowy city."
The Ace describes this ManCountry parallel area as "Lousy Real Estate" in English. Iirc, the japanese text more specifically calls it "事故物件" (stigmatized property, real estate where a crime, death, etc. has occurred), leading to:
3. The "place" is regularly associated with evil and especially death:
Nobody seems to be there.
Going there is tied in with Noelle's fantasies about flying away, which appears to euphemistically to refer to death
Its greyscale appearance in Man Country implies a connection with Goners, who's name is a euphemism for ghosts or dead people.
The Ace senses "Nothing but evil from this place".
It is treated within the game as not a real place, perhaps connecting it to the concept of "Going Nowhere".
Another possibility is that this area is related to the city December promises to bring Noelle to, which is paralleled in Cyber World. In the Weird Route (which this "other side" is most associated) we progress by freezing everyone in a city leaving behind a dead city.
So, collectively, what picture does the game paint of this landscape, The Place Where it Snowed. A snowy, plausbily greyscale, urban wasteland, most likely a city though hometown's town hall is referred to as a "city hall", making it questionable. It is a place where where people don't live and people shouldn't enter. And going there is repeatedly associated with death. This is unusual... and this is the only physical space known to exist outside of Hometown, at least during the events of the game.
Looking to other mentions of life outside hometown seems odd. Focusing exclusively on the present, Hometown is isolated from the rest of the world. Nobody has been to the other side of the lake. The internet is out, Tenna can only broadcast the same reruns on repeat since "a little while ago", Alvin only recently has stopped getting letters of condolence from fans of Lord of the Hammer. The Ferris Wheel only goes half way, a detail whose only purpose seems to be to obscure the other side of the lake. This has lead to the theory that the world Deltarune doesn't exist beyond what is visible, be it as a simulation or a diagetic video game. My original theories regarding the Place where it Snowed revolve around this, that it was a diagetic version of a glitched out of bounds area and the weird route being an attempt to restore a long removed "forbidden path" to the game, paralelling the dichotomy between The Legend of Tenna and the Mantle Game.
The thing is, I cannot believe Deltarune is purely a simulation in which only hometown exists... Why? Because (with the exception of the other side of the lake) Hometown's lack of communication with the outside world is very evidently recent. Asgore and Rudy went to college in their youth, Asriel went to college, Susie came from other towns/cities, Asgore has exotic flowers that explicitly don't grow in Hometown's climate. Repeatedly a world beyond hometown is implied to exist, at least in the past...
So Hometown has no contact with the outside world, and this isolation is implied to be an unusual and recent thing. The few crumbs we get of the world outside Hometown portray a cold and lifeless urban environment, one to which the very thought of being within is associated with death.
... an area that sounds like a Nuclear Winter? A dead world that can no longer communicate. ... And what did Gaster want to do with us...
In Short: Deltarune's hometown is "The Place Where it Rained", the only area of the world not affected by some previously unseen catastrophe, one who's affects resemble the aftermath of a nuclear war/incident (though might be a fantastical equivalent that ties better with the game). Gaster's motivation, and the goal of the prophecy, might be to restore the old world in some way. These wastelands on Hometown's periphery might be the fabled "World's Edge" described in the prophecy, but given the "Place where it snowed"'s relation to the weird route, it seems weird
NUCLEAR WINTER THEORY
This is... where my train of thought ends, there are further ideas I have that may be useful, though besides the connection with Snow and Death possibly foreshadowing Noelle destroying the world for good on the B-Side, these don't help form a solid conclusion.
I feel like this is only the first half of something proper, though of what I've been able to find myself this is where my research has left me stuck, unlike with Primordial Game. If any of yall have more ideas on where this branch may be heading, I am all ears.
