For high-level wizards who had truly set foot upon the path of magic, their own magical path was something they could speak of, yet also had to keep highly confidential.
It was like asking a successful businessman how he had succeeded. He could tell you empty platitudes about hard work and struggle.
Superficial success theories like seizing opportunities and daring to fight and strive.
At most, he might tell you about the journey of his own thoughts and feelings along the way.
But how to open up connections at the upper levels, the tricks to recognizing and employing talent, the core secrets of his own products, the channels for acquiring customers, how to manage a network of relationships, how to land safely after riding the wind rather than falling to his death on the spot, and so on... those things generally would not be mentioned.
But Professor McGonagall could speak to Roger about these things.
She had been Roger's guide into the wizarding world. Under her watchful eye, Roger had grown step by step from a child who knew no magic beyond prophecy into what he was today.
The vast collection of books that had laid the foundation for Roger's understanding of magical theory.
She had given them to him.
Transfiguration, the magic Roger was best at.
She had taught it to him.
The path of alchemy that had increased Roger's growth rate by an entire order of magnitude.
She had guided him into it.
Though they were nominally professor and student, strictly speaking, Professor McGonagall could absolutely be considered half of Roger's master.
Had this been the era of ancient wizards before Hogwarts existed, he could practically have been called her inheritor.
Therefore, Professor McGonagall held nothing back in response to Roger's questions, laying out every relevant detail of