The method is simple: the Path is a sequence of steps. Each step is a role. The role prescribes how to behave, what to do, and what to strive for. The Paragon is the one who has mastered all the roles of his Path and has become something more. He no longer needs to play a role — he has absorbed the essence of each into his very nature.
But the Path is not just a set of masks. It is a way of transforming the soul. The Paragon does not pretend to be someone — he becomes someone. Each new role is a new facet of his being. He does not switch between them — he contains them all simultaneously.
The transition between roles is the most dangerous moment. The potion helps to digest the new essence, to make it part of oneself. Without it, the Path is deadly. The neophyte can lose himself, dissolve in someone else's will, go mad.
The Church knows this. That is why they control the Paths. That is why they keep the recipes for the potions secret. The Paragon is the one who has gone all the way and retained himself. He is the ideal. He is the weapon. He is the future.
But the Church does not need too many Paragons. One is enough. One that they can control.