Tamiyo had approached Innistrad as a scholar, recording its moon and the stories that organised life beneath it. Her research placed Avacyn at the centre of the disturbance, but centre did not necessarily mean origin. Something beyond the plane was pressing through its most important structures.
Jace and Tamiyo confronted the angel in Thraben Cathedral and could not hold her. Avacyn adapted to their magic and carried the authority of every ward built around her name. Sorin arrived knowing that rescue was no longer possible. He unmade his own creation rather than let her complete the destruction of the people she existed to protect.
Avacyn’s death ended one danger and opened the plane to another. The angel had been a stabilising force even while corrupted, a final obstruction in a design neither investigator yet saw completely. Solving the visible mystery had removed the lock from the deeper one.