When you are trying to join a server with Thorium Bosses Rework with default settings, they cannot join as their game will crash.

Solution:

If you are trying to join a server with this mod and Thorium Bosses Rework, be sure to tell the host to go to Mod Configs -> Ragnarok -> Boss Config
Then, disable the first setting and move all the sliders to the right.

The config is as follows:

• Boss Stat Tweak - OFF
  
• Thorium Boss Rush - SLIDER TO THE VERY RIGHT
  
• Grand Thunder Bird AI - SLIDER TO THE VERY RIGHT
  
• Queen Jellyfish AI - SLIDER TO THE VERY RIGHT
  
• Viscount AI - SLIDER TO THE VERY RIGHT
  
• Granite Energy Storm AI - SLIDER TO THE VERY RIGHT
  
• Buried Champion AI - SLIDER TO THE VERY RIGHT

Not sure when will Ragnarok's dev fix this. All I know is its caused by their mod attempting to disable the boss reworks from mine.