1.16.5-36.2.5-8.1.0-RC1312 java.lang.RuntimeException: java.lang.reflect.InvocationTargetException

This seems to be a incompatibly between sponge and whatever mod owns this file frostedheart.mixins.json

I would report the issue on both mods GitHub pages.

If you dont know what mod owns that file, you can use my program of Mixin Detector to find it