Hew, Battleaxe

After slaying a young green dragon named Venomfang in the ruined village of Thundertree, the adventurers came across a tarnished and rusted battleaxe. When carried through forests and woods, it left its handler with a sense of wariness. The haft was inscribed, "Hew." In its tarnished state, any successful attacks against a plant-based creature dealt maximum damage.
By an involved process using distillation equipment and a solution of dragon's bile, the dwarf paladin, Azan Antar, restored the axehead to its former gleaming glory, revealing a series of ancient dwarvish runes etched into the metal. They told the story of the weapon's forging and revealed its final and most powerful secret.
When the word of invocation, "igni," is uttered by the battleaxe's wielder, the axehead erupts in blue flame. The next successful attack releases the weapon's stored energy into its target in a fiery explosion dealing an additional 3d6 fire damage. This ability will not recharge until the next dawn.