The Troll Blacksmith asks the Hero/ine to stain the head of his Pickaxe with Vampire bat's blood, by slaying 1Vampire bat. Vampire bats can be found throughout the Mining Caves stage. The Hero/ine must equip the Pickaxe and use it in battle (it will glow, as if enchanted, once you have succeeded). A good way to get the job done is to lower its health with a normal weapon, equip the Pickaxe, then try to slay it.
Once the Hero/ine returns with the Troll's blood-stained Pickaxe, the Troll will take his Pickaxe back (unless it's still equipped, but will leave any mined Dark Gold Ore untouched) and the Hero/ine will be rewarded with the choice to reforge 2 items of the same kind, into 1 level higher than the highest level item used in the forging process. The items must not be degraded, not be cursed, and must be identified.