How does soulbound work?

How do I know if I will get a white bag or something soulbound from a boss? Is it a set amount of damage you have to do to the enemy, or does it vary with the amount of players in a said realm or dungeon?
I've gotten white bags from Deadwater Docks before, but at some point I did more damage but didn't get a white bag.

This gets asked a lot.

It is not something published by DECA and it is more of a speculation and a lot of tests from different players but it looks to be related to the damage done and number of players in most cases

I think the most comprehensive answer (list of theories) you can find is here: https://www.reddit.com/r/RotMG/comments/46or1f/how_does_the_loot_system_work/

inside ROTMGBotzilla post