Hunt White Lion Magicians and White Lion Spellcasters around the Lost Mines to acquire White Lion'sMagic Scroll. Take this to TheletarPeralta at the Resistance Base.
Theletar Peralta: I knew it! I was right! NakanoAzusa: What does it say? Theletar Peralta: Their magicians cast a curse on civilians with weak Theletar Peralta: immunity against magic and ask them to join their clan Theletar Peralta: if they want their disease gone. NakanoAzusa: How could they harm weak civilians!? How dare they! Theletar Peralta: They must be punished. Defeat the magicians this time. Theletar Peralta: It's likely they'll have the curse scrolls.
Reminder Dialog
Theletar Peralta: White Lions are careful about what they do. Theletar Peralta: Not every one of them will have it, but that shouldn't Theletar Peralta: be an issue for you.