This method where one's spirit was sacrificed, to enhance one's powers, had existed within the Middle Realm from a long time ago. And this method if it was to be further segregated, would be split into two types. The first type would be as what Fan Zhuo had mentioned, which was the most direct method, that would turn a person into a mindless puppet, greatly increasing one's strength.
While the other type, was even more terrifying.
That method would raise a person's powers to a completely new height, gaining them powers that could crush a Purple Spirit.