After killing a group of goblins, the young man just starting to make a name for himself as Goblin Slayer finds a ring that emits a strange glow. In order to make sense of this item, he's introduced to an eccentric Arch-Mage, who then employs him in her quest to update the world's encyclopedia of monsters - starting with the entry on goblins. She and the young Goblin Slayer travel to the ends of the earth to gather information, and eventually reach an ominous dark tower...