He wanted to train it himself, but he didn't know where to start.
From the limited information available, Isaac only knew that this trait could only be awakened through one perilous transaction after another. But while Isaac had plenty of experience with transactions, as for "perilous"...
They were anything but!
On the contrary, he felt completely at ease during the entire process!
It was like coming home!
But things were different now. He had the Divine Spirit Book. He could have a new Wizard trade with an Outer God under his control. As long as the transaction was confined to the Real World—that is, by first summoning an Incarnation and then having them trade with it—it was a guaranteed success in another sense.
The only uncertainty now was whether a transaction completed in this manner would be judged as that of a Mad Witch...
'If so, it means the definition of a Mad Witch isn't that complicated. But if not, then things are about to get interesting...'
