Massive sledge with 3-pounder cannon built into the handle

Warhammer

Basalt + Obsidian head, solid iron cannon, leather-wrapped handle, cast-iron and bronze pommel with small carved grooves, handguard over hand-squeeze trigger.

Over 1,500 lbs

Can be recalled to and from The Hoard as need be.

Wyvern Fire ability charges a large blast of fire, cannon needs to cool down before firing again.

Heavier than originally thought, requires Earthbending to lift and wield properly.

Yama forgets that people aren't as strong as him, nor do they possess any Bending capabilities, which means most of his weapons are incapable of being used by anyone other than him.

Cannon is single-shot, with ammunition being created on the fly with the help of the Powder Horn.

Used only when fighting large monsters or powerful foes.

Head can be Bent to make other shapes, such as a greatsword, war scythe, buzzsaw, lance, or any crazy idea or amalgamation he can think of.

Obsidian is meant to provide extremely sharp cutting edge, fractures sharper than steel.

Wyvern Fire ability leaves the barrel red-hot, can't fire any shots until it cools down, risks damaging the weapon.

Effective range is about 1000 feet.

Attachments include a gatling gun, six-shooter barrel, handle to hoist the weapon. The cannon barrel itself can twist off, and the attachments lock in solidly. The gatling gun is powered by a hand crank, mostly for the aesthetic rather than function.

The trigger is a hand-squeeze, and can be lifted up to lock with the hand guard as a safety.