The rust creatures invade your world through rifts. What if, during a temporal storm, you get summoned through a rift into their world. A world full of rust and devastation (wink wink), looking much akin to the (story location spoiler)
In which you enter a totally different world occupied by sprawling towers of rust reaching for the sky, buildings distorted and rusted away, leaving you to roam the streets, though it would be more like running away from the hordes of rust creatures that occupy this world. You would have a limited time in this rust-world to loot as much as you can, probably really good or rust-world exclusive resources, before being summoned back to your own world. Each temporal storm, you get summoned back to where you left off in the rust world. Sort of like playing two games at once. Maybe your inventory even changes...? A rust-world only inventory and a regular world inventory? Sort of like what happens in the aforementioned story location.
I don't like how little stuff there is to do during a temporal storm... I wonder if it could be made more exciting. Or perhaps temporal storms can remain and this would be a totally different thing. I figured it would be insane to have two different games in one, one in the regular survival world, and one in a much more eldritch, perhaps slightly souls-like world. There would be a totally different progression path as a Seraph in the rust world, maybe making scrap tools exclusively to survive...? It would only be very short bursts that you would be in the rust world for, about how long a temp storm usually lasts for.
How the lore would work with this... I have no clue. I thought it would be an insane idea, anyway.
Feel free to take inspiration or build on this idea if you desire.
