Shattered World from Crusader Kings II is back in the form of this mod!
The option to shatter into counties, duchies, or kingdoms has been implemented by making a new Game Rule you should find rather easily at the top! However, this does not make a random new world, it just destroys every title of a certain tier.
WARNING: AS OF THE MOST RECENT UPDATE, THE WORLD WILL SHATTER ONLY AFTER YOU SELECT “PLAY”. YOU ALSO NO LONGER NEED TO DO THE HASSLE THAT WAS GOING INTO SINGLEPLAYER FOR HOSTING IN MULTIPLAYER.