Chaos energy is like Harnessed Energy (commonly known as magic energy, mana, essence, ect.). However, the difference between them is simple: Chaos energy is free-floating energy particles in the air.
When someone uses magical energy, it drains from their reserves in the soul. But, how do we replenish this energy? Does the soul create the energy? No. Instead, the body takes in Chaos Energy Particles from the air through the skin, which make their way to the soul. Once energy reaches the soul, it is readied for use and is considered Harnessed Energy.
When taking in Chaos Energy, you only take in particles of your element. When using different elements besides your birth element, you convert your energy into that type as it leaves the soul. However, the sould cannot convert energy entering the body, which is why you can only absorb Chaos Energy of your own type. Chaos Energy is absorbed rather slowly.
Note: Reifac and Dracim users regenerate energy 3 times as fast, and Shadesi users 2 times as fast.