Goblin Slayer Side Story II: Dai Katana, Vol. 1 (light novel)

"Not a soul knows how the death and destruction started. Only one thing is certain--it came from the north. Deep within the Dungeon of the Dead is where the Demon King resides, and the only hope humanity has of defeating this great evil rests on the shoulders of a handful of adventurers. This tale of Sword Maiden's past smells of ash and sounds like the ringing of bare steel"--