I was thinking about the myth of Bearfirth and how there was supposedly a god deep beneath the earth that she encountered and I wanted to propose a rough theory that popped up in my head:
The Salvation Engine is a god. The only solution Jonas could come up with to stop the unstoppable force of nature that was the Rot was to create a god to smite it from the earth. It's not what you'd expect a god to look like; from the Salvation tapestry, it evidently takes the shape of a massive machine with no face or arms or anything remotely resembling a humanoid, but it is still a god, and it still hides deep within the earth where it was constructed centuries ago. It would explain why the empowered humans it created are called seraphim; the humans involved in the god's creation became its angels.
It's possible that the Engine ended up kind of being like Vintage Story's equivalent to GLaDOS from Portal, in that it was a being they created and then, in Jonas' words, "awakened". In Portal's case, it was a giant computer containing an AI that instantly went rogue and killed everybody, but in the case of the Salvation Engine in Vintage Story, it's hard for me to say exactly what it did upon awakening.
Think about the eidolons; they're robots with some degree of independence - at least enough to go mad and start killing their creators, as does the one in the Archives we encounter. I don't think it'd be a stretch to think that the Engine is something similar; an artificial intelligence - a robot, essentially - but instead of being a soldier/guard/worker like the eidolons were, it's a god with the abilities to warp space and time.
When Bearfirth fled beneath the surface, she actually stumbled upon the facility containing the Engine, and the Engine spoke to her. I would elaborate more on the possibility, but I 'm not confident I know the game's lore well enough.
