There's a theory that Heatran was the inciting incident of the continent towing myth. Volcano threatens Sinnoh, Regigigas moves Sinnoh and/or the volcano out of the way.
Or, to put each on par with one another, maybe Regigigas moving the continents released energy within magma chambers deep underground which resulted in more births of Heatran. The Heatran in turn then start digging more tunnels and chambers to make the magma flow, which results in the creation of more tectonic plates forming thus easier for Regigigas to move the continents around. As with it easier for Regigigas to move the continents it begets more Heatran who dig more making the continents easier to move until Regigigas was finished moving around the continents and went into a deep sleep and the Heatran just maintained the planet's magma flow.
I remember there was other lore scattered about the Tundra, though, and I'm not sure the timeline necessarily lines up. But it's been a long time, I might be confusing some things.
The only "issue" I see with Calyrex's battle with Eternatus as soon as it arrived to the planet is that it would have happened 20k years ago. After the battle it awoke weakened in ancient Freezington where the people there helped it and thus it then helped them. 20k years seems a bit too far back for that, so instead I think the events happened like this:
> 20k Years Ago: Calyrex came into being and "ruled" the Galar region. Back then it was very powerful, likely power equaling the 680 BST mascot Legendaries, notably without needing the Wild Horse(s) which may or may not have existed. The Pokedex entries for its Rider forms mentions Calyrex at such power level can see the past & future as well as, at the very least, teleport something as large as an entire landmass.
20k Years Ago: Calyrex foresaw a meteorite crashing down in a forest and teleported said forest away, likely to where the Crown Tundra now resides. Of course this meteorite was Eternatus, however having just crashed onto the planet it likely wasn't active. Still, its landing setup for the creation of the Crown Tundra by forcing Calyrex to move an entire forest to the cold south.
20k Years Ago - Before 1st Darkest Day (3k Years Ago):
- Humans became a more active presence and power, forming civilizations and "industrializing" (for lack of a better word, what I'm trying to get across is that humans built themselves up using their intelligence and tool use to invent more complex infrastructure and economy; basically what separates us from other animals or Pokemon in this case).
- With now a forest to gain resources from, people moved to the the cold south and formed basic villages, one being Freezington.
- Calyrex kept "ruling" this entire time, likely watching humans rise up (and possibly even saw in the future people taking over rule of Galar).
- It was at this time that the Wild Horse(s) likely came into being as it was said to "rule" the Crown Tundra for a time (and terrorized the people of Freezington and likely any other human settlement that tried to setup there). Its/Their creation could have been as early as the teleportation event, created from residual energy from Calyrex, thus explaining the connection between it/them and Calyrex and how Calyrex gains power from riding it/them later on.
1st Darkest Day/3k Years Ago:
- Eternatus wakes up likely someplace near the Crown Tundra (can't see Calyrex moving an entire forest THAT far away from where it originally was) and starts causing chaos.
- Calyrex goes to fight Eternatus but is defeated and severely beaten. Calyrex barely escapes with its life while Eternatus goes north. This effectively ends Calyrex's reign.
- Eternatus is defeated by Zacian & Zamazenta and people fully take over as the rulers of Galar.
1st Darkest Day/3k Years Ago - SwSh's Present:
- Calyrex shows up in Freezington severely injured and weakened. The people there nurse it back to health and, to return their kindness, Calyrex uses what's left of its power to make the land more fertile and defended them against the Wild Horse(s). At some point the people make the Reigns of Unity that Calyrex was able to use to tame the Wild Horse(s) and ride it, regaining a lot of its power that it uses to enrich the Crown Tundra becoming a sort of local deity.
- This however was only temporary as Calyrex loses much of its remaining power and the Reigns of Unity either are lost or break freeing the Wild Horse(s). The Wild Horse(s) seemingly go into hiding/seclusion while the land turns back into a cold & mostly infertile wasteland. Unable to face the people of the Crown Tundra out of shame, Calyrex hides and watches from afar, waiting for a someone that could help it tame the Wild Horse(s) once again to regain its power. The people of the Crown Tundra, which narrows down to just those who live in Freezington, start forgetting Calyrex as it becomes a vague legend.
I'm going to assume I don't need to post what happened during the Crown Tundra DLC?
Where can you find Stonjourner? Not only is it not found anywhere near this town, it's also one of the Pokemon they chose to be version-exclusive for some reason. So if you have Shield you can come into this town, see all this Stonjourner related stuff, and then it turns out you can't actually get it. I know that "version exclusives bad" is preaching to the choir but this one is especially egregious.
Edit: Being so early in the game, having a single-stage's BST is a bit of an issue. Still, they could have made it possible to obtain around this area by giving it a prevo or designing the region so that the Stonehenge stuff is later in the game.
Or let it be catchable in Turffield but in a location that's only accessible later on, like there's a ruins location that's normally inaccessible to the public (maybe closer to the Geoglyph) that you can see NPCs and Pokemon there hinting you can go there. While the gate remains permanently closed, once you get the Water Bike you can use a pond right next to it to go around the gate (don't worry, no one really cares your trespassing). In addition to some Trainer Battles there's also Wild Pokemon, including Stonjourner.
Least we forget Bellossom in Gen 7...
Someone else feel free to post the cutout stand of the Hula dancer with Bellossom in the Heahea city welcome center.
According to Bulbapedia, Heahea city was founded by Kanto and Johto trainers, so there's a possible explanation. Doesn't explain the occasional NPC throughout Alola with a Bellossom though.
Or made an Alolan Bellossom (and I guess also an Alolan Vileplume).
Seriously, while I like the new forms of Dialga and Palkia as a duo, they're not Origin forms. They have no interest in maintaining aesthetic cohesion with Origin Giratina, they don't bother at all with the role reversal stat swap of Origin Giratina, they don't change their abilities like Origin Giratina. Even their lore is completely different from Origin Giratina. Game Freak could have called them literally anything else and I would have been fully on board with them, but they called them Origin forms when they just aren't.
I'm so glad the stock art actually makes them look better then the model renders we first had of them.
ANYWAY, while they probably could have just called them "Alpha Forms" and called it a day... at the same time I wonder if calling them "Origin Form" just like Giratina's is intentional. Cause, the thing is, they ARE different. O-Giratina is the form it naturally takes within the Distortion World, aka its domain (or has an object that resonates with the energy of the Distortion World like the Griseous Orb). Meanwhile O-Dialga and O-Palkia are forms they took in order to essentially impersonate Arceus, aka the "Original One". They're all "Origin", but a different sense/definition of the word. And that's just it, "Origin" is a word, a descriptor made by people to just describe these form changes. Giratina, Dialga, and Palkia don't care what the form is called, all they care about is that its a form they can change into to adapt to their environment and/or obtain more power.
Heck, if you want to look at the bigger picture, these likely isn't even their "true" forms. Cause their true forms are formless, they're a cosmic force, an omni entity and the bodies we see are just avatars they're using to interact with the material world. Which leads into
R_N's comment:
They fit "Origin" way better than Giratina. It's a little weird that Giratina was "Origin" to begin with because it was cast into the distortion world later, as punishment. This being its "original form", the thing intrinsic to calling something "Origin", is...weird, in that regard, since theoretically its the form it took to properly adapt to a gravity less strange world.
now of course the easy hand wave here is that is Giratina's true form and it just happened to align properly with the Distortion World's properties (well i mean it WAS Arceus' doing, so...) or maybe the DW was ALWAYS Giratina's realm and Arceus just locked it away in there, but Origin just being a catch all for their original true forms works more for the pair.
So all that said, I'll also say that Dialga & Palkia being the goodytwoshoes who given the chance to form their own forms in their own realms tries to imitate Arceus while Giratina purposely doesn't, is pretty flavorful. "no fuck YOU dad"
Is that lore from Legends: Arceus? I haven't finished it yet (I'm taking my time, I find just exploring and casually finishing Dex tasks rather calming) though I know most of the spoilers (for me its the journey that counts).
Anyway, it's very likely that latter point is what happened. Arceus likely created an avatar form first cause when creating a universe it's kind of handy having a material form to check to make sure things are working as intended. Arceus then creates Dialga to control time, Palkia to control space, and Giratina to handle anti-matter (with Arceus representing "matter"). This setup essentially makes Giratina a direct opposite to Arceus, which makes it angry, but at the same time means it too probably needs a material form if it's to do its job (though, unlike Arceus which took a form of a solid-looking quadruped mammal, Giratina made its form more gaseous and slender so it could maneuver better in a place which has its own physics). Dialga and Palkia didn't need material forms to do their job and MUCH later, when it came to a point where it was decided they required material forms, since the forms were more for presence than utility they copied Arcues form to both honor it and maybe see if they could obtain some more power while doing so. Not sure why they would then pick their "normal" forms after that, maybe discovering they didn't really get any extra power they decided it would be better for them to have a more unique appearance so that Arceus alone has it's "quadruped mammal" look (unless this is something they explain in Legends: Arceus).
EDIT: Except, no, it doesn't make sense for this to be their "Origin" form as these forms are directly derived from their normal form forced into an Arceus shape. To make the theory work, maybe Dialga & Palkia had their normal form shape but it was never a material avatar, just energy compacted into those vague shape. So when it was time to make a material body, they took the general vague shapes their energy bodies would take but molded it into an Arceus shape. When that didn't do what they quite wanted they then just had a material form based on their normal shape. So it's "Origin" only in the sense that's what they decided their first material bodies to look like. Yeah, I guess that works... or, you know, GF can STOP SAYING NEW FORMS ARE WHAT A POKEMON WAS MEANT TO LOOK LIKE!