I finished the incantation and dropped the green stone on the mirror. Rather than causing it to shatter, the stone vanished into the mirror. The surface rippled as if I had dropped the stone into a still pool of water. The reflection in the mirror began to change as the ripples settled and I found myself unable to look away. Once the motion had ceased, the room showing in the mirror behind me was completely different. I turned and saw that I was in the study of my long dead master. His corpse grinned at me from his favorite chair.