Spirits

Spirits, also known as souls are what identify each living being as an individual. Everyone who was born naturally has it. A soul is born in the other-realm from the other-energies each time when new life is born in the mortal realm. People, animals, even trees have souls.

Spirit/Soul is what allows people to use Chi and Will, as both are abilities that use other-energies. The soul is their connection to the other-realm. Everyone's spirit is equal and technically has unlimited access to other-energies, however the mind and the body of the user will always limit them from gaining limitless powers.

When a person dies, their soul remains in the other-realm. A soul's connection to the physical realm can be repeated about 4 times without memory loss, which enabled resurrection for two to three times. It isn't guaranteed that a resurrected person would keep their memories however.

In case of a reincarnation, the soul becomes a blank slate again. No memories remain, and the soul becomes pure. Even so, it is the same soul that once was another person. There is no limit to how many times a reincarnation may happen.