Threatened?

"Soul Bonding Method?" Vale repeated as he had never read or heard anything like this before. Nevertheless, it sounded cool, so he expected this method to be more beneficial than the one he was using.

"That's right… Do you value that Mystical Item you sealed?" Professor Morton asked suddenly.

"Of course. It's really important. I think I will use it more often in the future." Vale answered after some thought.

"Then, that's perfect. After all, the Soul Bonding Method isn't just a Sealing Method. It's also a method to properly control Mystical Items. I'm guessing that the item you needed to seal was probably too strong for you, or you can't handle its adverse effects." Professor Murton said.

Vale nodded at this since that was indeed the case. The Divine Sword wasn't something he could control at the moment. Perhaps there was a ritual or requirement to make it docile, but he had no way of asking Tracie about that right now.