The great collapse occurred on November 9, 204 AD when Zhang Jiao was able to successfully complete a spell that allowed to tear the veil between the mortal and spiritual plains granting him complete control over the destructive power of the animistic yokai, the warped and wicked oni,as well over the common soul of a fallen warrior. Being able to control such beings granted undeniable command over life and death granting access to create an army of undead soldier using the power of spirit world.