Lost, and Urgent Matter

All William had was his steel sword, his demonic sword, and the clothes on his back. His backpack with his supplies was gone. Not only that, but the magical tomes he had borrowed from the school's library were gone too.

"Damn it!"

He had brought the tomes to study during his time away from the school, as he didn't want to lose any practice time. What would he say to Tholfnir when he got back? That he had lost the precious tomes? And that was assuming he even made it back...

William walked a few steps and looked around. He was on the peak of a mountain. It was very tall, and freezing cold. The mountain had no discernible path leading up to it. The only way William had managed to get there was by griffin.

This meant it was essentially impossible for him to descend. What would he do in this situation?