crash-2021-09-05_13.23.42-client.txt
latest.log

thank you! The fix is now released on curseforge.

I never seen this crash before. Something has a field State but it isnt a json object. I'll try and harden the mod against these kinds of assumptions. Would you be able to provide me the exported modpack profile so I can try and test it on my end?

You can give this test jar a try (be sure to unzip this folder to get the jar). See if that fixes the crash
world_blender-1.16.5-4.0.1b-forge.zip

That did fix the crash, I also narrowed down the crash to the newest version of Mystical World/Mystical Biomes