Soul Integration

Soul Integration (憑依合体) is the fundamental shamanic ability of the Shaman King series, in which a shaman willingly becomes a vessel for another spirit to possess.

About
When a shaman faces situations they alone cannot perform, they can make those tasks simpler by finding find a spirit ally nearby then can voluntarily lend their body to for the spirits to possess. Unlike regular spiritual possession, the process is a course of voluntary subjection to which the shaman must be able-bodied and strong-willed to synchronize with that spirit to become one in order to unlock their full potential and performance. During that state, the shaman appears to have developed another character to which it is the spirit themselves which his/her personality, knowledge and previous life experience in tact.

Through the basics, many shamans tend to use human ghosts for the job because of how easier they can cooperate as the shamans themselves are also human. But for a shaman to become an all-rounder vessel for various spirits and of higher-class, they must vigorously train their bodies while possessing a strong state of mind to avoid losing consciousness by the spirit's possession as they sometimes can be more independent than regular ghosts.

The only advantage of Soul Integration before the introduction of Over Souls is that they consume less Furyoku which is beneficial for preserving the shaman's strength for tougher situations with the method as a way out.

Weaknesses
During integration, it is a unison state where two minds act as one, in which the shaman's body must be physically fit to reduce the amount of stress caused by the addition of another soul. Otherwise, the body will tire down if non-shamans were to be possessed by force, or cease functioning meaning death if the worst case happens.

Furthermore, the point of Soul Integration is displaying the strength of the spirit-in-possession, but not the shaman's own powers.

Types of Integration
Generally speaking, Soul Integration is not limited to the shaman themselves. If they possess enough Furyoku, they have enough power to integrate souls into other organisms, in which the effectiveness depends on how fit is that vessel enough.

Inanimate Objects

 * Dàoshì, like those of the Tao Family, integrate souls into corpses in order to create Jiang Shi, where the matching soul and body equals 100% Integration which results in the performance of their original peak strength.

Animal Integration

 * Shamans can integrate souls of non-humans such as animals or other living creatures, such as when Tao Ren integrated Bason's horse, Hei-Tao, into his trained shamanic horse, Bái-Feng.