What does the man from the mountains believe about Duny?

Are you referring to Ogion? Ogion is Ged’s first master after he discovered his magical powers. Ogion comes to the village where Ged was staying after he heard about the boy who was so affected by the magic he was doing that he ended up in a comatose state. Ogion brings Ged out of that state and help him control his powers. Ogion then takes Ged as his apprentice but Ged is unsatisfied with the things Ogion teaches him.