Soul Integration

Soul Integration (憑依合体) is a fundamental shamanic technique, in which a shaman willingly becomes a vessel for another spirit to possess. This technique provides the spirit a physical body with which to resolve their unfinished business, allowing them to rest in peace.

About
For this technique, the shaman transforms the spirit into a small orb—called "Spirit Flame Mode" (ヒトダマモード)—and then shoves the orb into their chest, allowing the spirit to control their body. Due to the presence of two souls in the body, any conflict or disparity between them can lower the technique's capabilities. Some shamans overcome this weakness by completely subjugating their spirits. However, if the shaman and spirit unify their thoughts, then they can also achieve 100% Integration.

When a shaman faces situations they alone cannot perform, they can make those tasks simpler by finding a spirit nearby with the necessary skills. 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
Soul Integration, especially when drawing out 100%, puts heavy strain on the shaman's body; therefore, the shaman 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.

Normal shamans are limited to the spirits in their immediate surroundings, so if a shaman wants to utilize a spirit away from their burial site or haunting, they must carry around a portable memorial in which to house the spirit. If the spirit is sent to the afterlife, then the shaman will be unable to use Soul Integration, and if the memorial is taken by another shaman, that shaman could subjugate the spirit as their own. Itakos, however, can summon a spirit from anywhere, even if it has moved on to the afterlife, and channel it into another person, a process known as Itako-Style Integration: Spirit Channeling (イタコ式憑依術 クチヨセ).

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.

Cloud Integration
A shaman who can access the Cloud can integrate with the copy of a spirit, whether or not the original is still alive.