Akmon, Hammer of Purphoros

Weapon (warhammer), artifact (requires attunement)

Purphoros's hammer works wonders and disasters, the god of the forge using it to craft ground-breaking marvels and dangerous inventions in equal measure. Purphoros rarely bestows Akmon on mortals but occasionally leaves it unattended at his forge in Mount Velus. When Purphoros does permit a mortal to use the hammer, it's usually so they might bring an important work into being, wreck a force of destruction, or forge something remarkable somewhere the god isn't welcome.

Hammer of the Forge. This magic warhammer grants a +3 bonus to attack and damage rolls made with it. When you hit with an attack using it, the target takes an extra 3d10 fire damage.

Reforged. While holding the hammer, you have resistance to fire damage and are immune to exhaustion. Additionally, you have proficiency with smith's tools and have advantage on all ability checks made using them.

Blessing of the Forge. If you are a worshiper of Purphoros, you gain all the following benefits for which you have the required piety:

Piety 10+. The hammer has 1 randomly determined minor beneficial property.

Piety 25+. The hammer has 1 randomly determined major beneficial property.

Piety 50+. The hammer has 1 additional randomly determined major beneficial property.

If you aren't a worshiper of Purphoros, the hammer has 2 randomly determined minor detrimental properties.

Magic of Creation. You must be attuned to a magic item of rare or higher quality and another magic item of very rare or higher quality, each created by your own hands, for the following effects. The bearer can spend 1d4 weeks enchant magical weapons to increase their attack and damage roll bonus by +1, up to +3. Spells. While the hammer is on your person, you can use an action to cast one of the following spells (save DC 18): Animate Objects, Heat Metal, Fabricate, Magic Weapon, Mending, Shatter. Once you use the hammer to cast a spell, the spell can't be cast again from it until the next dusk.