It'll try to convert your map, countries, cultures, religions, rulers, heirs, advisors, vassals, empires, and a few other bits as best as it can to fit into, y'know, a different game with different rules. Made by fans who did this with Crusader Kings 2 before, the CK3 To EU4 Converter lets you generate a new EU4 starting scenario from a CK3 save.
You could also then use another tool to take that from EU4 into Victoria 2, then into Hearts Of Iron 4 with yet another tool, converting the same world across one millennium-long 'megacampaign'. And you can do that thanks to a tool which transfers a CK3 world into Europa Universalis 4, picking it back up in the Paradox grand strategy game set in the following era. What to do when you've completed a Crusader Kings 3 campaign? You could start over as a new ruler in a new place, I suppose, but isn't that negligent? A truly responsible leader would steer their nation through the middle ages, the Victorian era, and World War 2.
