My modified config keeps crashing the game with:
Caused by: java.lang.IllegalArgumentException: Level 20 does not have 1 requirement
at com.rwtema.monkmod.config.MonkConfiguration.load(MonkConfiguration.java:200)

This is the custom config:
https://pastebin.com/RKwQNZLi

This was my fault. Error in how I wrote a thing.