The Spirit War began when enslaved spirits rebelled against the people of the Zhari region.
Early in the reign of the Zu Empire in the Zhari region, it's people began studying the supernatural forces that spread across their land, and from this study they began to find ways to weaponize the spirits. With the discovery of magic abilities able to trap spirits within items and exploit their powers, they began enslaving and abusing the spirits. This created hundreds of evil Kami.
The evil Kami and angry Spirits began to rebel soon after, beginning the Spirit War. Primal spirits did not take part for years, instead mending the earths wounds caused by the war. Before long, the evil Kami began attacking the primal spirits as well. Dwindling in number the primal spirits were split between new evil Kami and those who could not tend to the land and were forced to abandon it in favor of survival, leading to the Age of Famine.
Throughout the Age of Famine, the spirits recovered and retreated back into the spirit world. Once the people of the region resumed the practice of Shin, the primal spirits returned, bringing with them life back into the land. However, the spirits have since been angry with mortals and dispite constant prayer and respect, relations are rough.