There are types of spirits in the world. Some are wandering spirits who have fulfilled their wishes and are unwilling to leave. Some are earth-bound spirits whose souls are trapped by people after death and are never allowed to leave a certain place. Some are ghosts with powerful grudges that refuse to leave after death and cause trouble in all directions. When a spirit threatens human normal life or even life, humans will send soul masters to save the spirit and reincarnate.
Purpose: redemption