"How could it be such a coincidence that it collapsed just as I was thinking of leaving?"
Shard, coughing and steadying himself against the door to stand up, checked to confirm that the path he had come by had indeed collapsed, and couldn't help but feel puzzled.
But thinking about it, it seemed there had been other coincidences tonight that led him straight from Sophia's Mansion to this underground iron door. For instance, in the tavern, he heard the professors' conversation after using Arcane Technique three times, and thus directly learned even more secrets.
That could be chalked up to luck, or to coincidence. And if it was the former, Shard somewhat understood what had happened:
"Could it be the Puppeteer's Notes that brought me here? But last time it was a whole night of good fortune; this time, it seemed to merely provide the convenience of getting here."