Dumbledore had always suspected that Vaughn's ordeal while roaming the aether had been caused by Voldemort's curse. After all, he held the title of Defence Against the Dark Arts Teaching Assistant, so it made sense that he could shoulder some of Isabella's curse.
But that had been an isolated incident. Vaughn had suffered no further mishaps afterward.
Thus, they had no way of knowing whether other staff involved with Defence Against the Dark Arts would also be affected by the curse, aside from the official Defence Against the Dark Arts Professor.
If someone else took the teaching assistant position and suffered an accident as Vaughn had, Dumbledore would certainly believe Voldemort's curse was responsible.
Yet Vaughn himself was highly unusual. Both Li Nanyu's words and the Centaur Tribe's prophecy indicated that Vaughn could step outside fate.
But the affair with the Diary had seen fate make a fool of Vaughn, and linking all those clues together only made matters more bewildering.
Dumbledore suspected that Vaughn had initially been unable to escape fate, and only later, through some particular catalyst, had become the variable Li Nanyu spoke of.
Viewed through that logic, everything made sense. Hiring another Defence Against the Dark Arts teacher should indeed help shoulder Isabella's curse, just as Vaughn intended.
Vaughn, however, saw things differently, because only he knew that the real reason he was a variable was that he had transmigrated here. His soul did not belong to this world.
He felt that fate had toyed with him before, and Voldemort's curse had taken effect, largely because his influence on this world had not yet been great enough.
Only when the Potions Exchange got fully underway and the changes he had driven began to unfold had the variable he represented become enough to shake fate. Still, both