So, what is it? How do you earn it? What are the qi-related limitations?

Qi is experience, once you gain enough qi, you will earn a new belt, qi-related limitations involve items, you have to have a certain amount of qi to use certain items, (I.E - Elf joints, custom belt title)

List of Belts
*0 - 19 Fights - White
*20 - 49 Fights - Yellow
*50 - 99 Fights - Orange
*100 - 199 Fights - Green
*200 - 499 Fights - Blue
*500 - 999 Fights - Brown
*1000 - 1999 Fights - Black
*2000 - 2999 Fights - 2nd Dan Black
*3000 - 3999 Fights - 3rd Dan Black
*4000 - 4999 Fights - 4th Dan Black
*5000 - 5999 Fights - 5th Dan Black
*6000 - 6999 Fights - 6th Dan Black
*7000 - 7999 Fights - 7th Dan Black
*8000 - 8999 Fights - 8th Dan Black
*9000 - 9999 Fights - 9th Dan Black
*10000 - 14999 Fights - 10th Dan Black
*15000 - 19999 Fights - Master
*20000 - 49999 Fights - Custom
*50000+ Fights - God

Every time you play a game you get QI. No matter if you win or lose. If it is a draw, then neither player gets any.

QI can unlock newer items for you to use.

Elf is for master belt and up, not custom belt and up.

So here are the main qi items:

Typhon: 5th dan black belt
Pure, alpha imperial: 10th dan black belt
Elf: master belt
Demon, void: custom belt

I was giving examples of qi related items.

What is Qi?
It sort of counts the amount of the matches you've played
You earn it by playing matches
You use Qi to unlock items.

You read threads in future before posting in them. ~Fee