Separate rust dimension from overworld

[𝔼𝕟𝕥𝕚𝕥𝕪]

Generate the world twice to have two dimensions with identical landscapes overlapping with each other. Buildings and terrain manipulation in one dimension are separate from the other. Step into a rift portal to enter the rust dimension, the only way to leave is through another portal, watch out for the rift closing up behind you or you may find yourself stuck longer than intended. Instead of taking damage when temporal stability reaches 0%, you will faint and then wake up in the rust dimension where you must survive the horrors and seek out a rift to escape. Puzzles could be added that are solved by going between dimensions. For example, a building with barricaded shut doors in the overworld is inaccessible and the only way to gain entry is to brave a trip into the rust dimension where the doors and other obstacles have long since decayed away. Implement a Jonas device that generates a portal, allowing to freely travel between dimensions.

[Thorfinn]

Interesting idea. I'd be a little hesitant to double mapgen time, but swapping out the atlas seems like it should do roughly what you are looking for. Might not even have to do that -- just play around with the sepia settings to get something looking similar to a temporal storm.