The Otherworldly must behave as their stage dictates, until the power becomes part of them. Until the potion is digested, the bearer is vulnerable: the power is already there, but there is no control over it yet.
The path roles are public: the Bard performs before people and leads them, the Notary witnesses and certifies someone else's truth, the Priest of Light preaches and purifies. Here, one cannot digest the potion in solitude — one needs someone to whom to address.
The method long remained the knowledge of a few: the church hierarchs were in no hurry to reveal it, and many Otherworldly rose blindly, paying for it with their sanity.