There are multiple characters with the name Luther. See Luther for disambiguation.
Luther is a guard in the kingdom of Merica. He trades one of his fingers to Magon Coifer in exchange for Torg's hat and goggles. On weekends, Luther works as the Ferryman of Yffi. Anyone desiring the Book of Güd must pay him all their gold to ferry them to the cave where it resides, despite there not being any water around the cave.