The Lord of Rust Mountain

Two years had passed since he left the City of the Dead, and Will was seventeen by count. As a lord, he developed "Torch Port, a river port of light", and gradually the people's activities and smiles returned to "Beast Woods". However, out-of-season flowers bloom profusely, and an abnormality is discovered in the forest. Will and his friends head into the depths of the forest to solve this problem, and receive an ominous prophecy from the king of the forest. "In the Iron Rust Mountains, the 'Fire of Black Calamity' will occur. The fire will spread, or it will burn everything in this land." What is the calamity that sleeps in the ruined dwarven city of Tetsusabi Sanmyaku...!?