The Faraway Paladin (Manga) Omnibus 4

After a thorough restoration under the leadership of Will, the city of Torch Port is now home to diverse folk from all over the world. Its newest citizens are dwarves from the Rust Mountains, former warriors turned vagabonds by the fall of the Iron Country.

Will sets out to learn about their past, hoping not only to help them out as much as he can, but also to investigate rumours he's heard about an imminent threat lurking in the mountains.

Then, a mysterious prophecy shakes Will's resolve: "Thou shalt challenge the dragon with the protection of the god of the flame and die defeated, thy purpose not fulfilled."