Magister Iris:
Thank you so very much!
I've found out that the Langk Lizardmen use a Dragon Tooth to perform their sorcery. I'm not sure whether or not it's actually a tooth from a dragon, but their sorcery is strong, and has evolved from ancient times. The document Magister Rohmer sent me is from that period.
The document explains that only by using the same medium can its power be canceled. The more of this medium we possess, the more power we'll have over the sorcery. Unfortunately, I don't have enough dragon teeth yet. While you were away, I inventoried my supplies and have only 50 of them. We'll need some more if we're going to cancel that sorcery.
Go to the Langk Lizardmen dwelling, get 50 dragon teeth and bring them to me. Only the Shamans and Leaders have the teeth. You'd better get started! Good Luck!