During the reign of the Shadow Realm whose unrivalled king of darkness dominated over the Mortal Realm, there existed five classes of demonic possessions.
Before the Shadow Realm's demise, its residents inhabited the bodies of mortals and cultivators in an attempt to reproduce or drive their hosts to irrecoverable corruption.
Some mortals and cultivators were salvageable depending on the degree of corruption, while others succumbed to the demonic energies that blighted their dantian cores.
The five stages of demonic possession were divided into five degree classes beginning with the basic Corruption class, followed after it was the Malevolence Class, Chaos Class, Desolation Class and Annihilation Class.