How would I destroy the world with a decision?

[ThothTheScribe]

I'm curious as to what would go into making a decision that would convert all of the counties (except for a few) into wastelands/ruins? I think it'd be neat to be able to rebuild a ruined world from just a few major settlements that are large enough to survive the "Second Doom" or what have you. Was wondering if anyone could tell me what files I could copy, gut, and repurpose to make this a thing.

 

[Orinsul]

It'd be better to do it through modding the files rather than in game, so you'd cut out all the unneeded characters and speed the game up.

 

[ThothTheScribe]

So editing the history files and making "Ruins" own most provinces?