So I was fighting nighttime Providence and it decided to leave mid battle several times in a row. Funnily enough, Fanny seemed to think I killed it and gave new dialog along the lines of "these guys in crags now got upgrades and new drops" or smth like that.
Okay, I thought, decided to fight the normal one and died. Then fanny started talking about "our 20th anniversary" thing and transported me to a desert, covering the whole world.
That thing is called Profaned desert and it actually spawns after losing to Providence. When I say spawns, I mean it literally replaces the whole world with useless blocks and destroys all unnatural blocks, places by the player, at least according to fandom wiki.
Although devs say that the mod isn't 100 percent accurate with the fandom wiki, wiki.gg doesn't even have information on Profaned desert, it only acknowledges the blocks that spawn there and the fact it's generation could be disabled in Anomaly 109 (wish I knew that sooner).
So as far as internet tells me, and this is the fandom wiki thats telling me this, this state is irreversible and my 150+ hour world is lost to fking Providence and her infinite desert

UPD: So i reloaded my save and luckily that desert thing did not save. I don't know if my autosave didn't work for 30 mins straight or is it specifically programmed that way to return you to your world after reloading, but for others, that may have that spook, i'm leaving that here

UPD2: Yeah, probably another good to mention on the matter, you can disable Profaned desert generation in Anomaly 109 menu