The Great Furnace (Patreon)

Maul, very rare (requires attunement)

This Maul is built with an intricate pressure system fueled by elemental gems. You gain a +2 bonus to attack and damage rolls made with this magic weapon. This weapon can uphold five charges at a time and gains one charge every time it hits a hostile enemy. If you expend more than five charges before making a long rest the weapon overheats. Roll a D4, if the result is 1 the elemental gems are damaged and the Maul loses all its magic properties.

Jet strike. You can use your action and expend one or more charges of this weapon to release an explosion and use the force to move up to 5ft for charge spent without provoking opportunity attacks. When you arrive at the new space, you can make an attack roll with advantage against a creature within 5 feet of you as a part of the same action. On a hit, the target takes an extra 1d6 fire damage for charge spent.

Wheel of fire. You can use your action and expend one or more charges of this weapon releasing a hot stream of vapor, and making a full rotation. All creatures within 5ft of you must make a DC16 Dexterity Saving Throw or take 1d6 fire damage for charge spent, or half as much damage on a successful save.

Overhaul. When you hit a creature within 5 feet of you with a melee attack using this magic weapon you can choose to expend 5 charges at the same time releasing a roaring explosion of flame. Each creature in a 20-foot-cone starting at the target of the attack must make a DC16 Dexterity Saving Throw or take 8d6 fire damage, or half as much damage on a successful save. The creature hit by the attack makes the Saving Throw with disadvantage.