Hammer of the Azer

Weapon (light hammer or warhammer), uncommon (requires attunement)

This magic weapon features a dwarven face on its head. When swung, the face's mouth opens up, and a plume of fire erupts from it. A creature hit with this weapon takes an extra 1d4 fire damage from the attack; when you roll a 4 on this fire damage die for the first time on a turn, roll another d4 and add the result to the total fire damage dealt.

Furthermore, if you're a dwarf, you can use a bonus action to cause the hammer to fly to your hand, provided it's unobstructed and within 60 feet of you. While you're holding the hammer, the hair on your head becomes fiery: this effect is illusory and harmless.

The dwarves knew how easy it was to give into the flame. The hungering anvil sung its siren's call with every strike of the hammer, and the forge's tongues of flame and sparking embers beckoning them onward.
But even the hardest stone can melt, and over time, some dwarves did too.