The Cadaver Demon was ideal for a refined corpse. Not only was its body incredibly formidable to the point where common magic treasure couldn’t harm it in the slightest, but just a small amount of the corpse fire and poison that it produced could immediately kill a cultivator. It has to assumed that Han Li refined it just afterwards. The refined Sovereign Devil Corpse appears after his travel to the Far West.
The Sovereign Devil Corpse was lost in Devilfall Valley after the fight against the Elder Devil. Han Li's Second Nascent Soul then took control of this corpse and tried to rebel against its main body. His failure was followed by the destruction of the Sovereign Devil Corpse by the Triflame Fan.