+1 Adamantine Maul

Whenever you hit an object with this weapon, the hit is a critical hit.

  This weapon is incredibly heavy, even by adamantine standards, but that does come with its perks.

Spin to win

You can, as an action, choose to make one massive swing with your adamantine maul, dealing massive damage. Choose whether you swing clockwise or counterclockwise. Make an attack roll against the first creature or object you encounter when following your swing direction. If you miss or kill/destroy your target you can keep the swing going. Make a new attack roll against the next creature or object and again you can keep going if you miss/kill/destroy the target. This stops once you have landed a hit that didn't kill, when you have completed a circle, or when you choose to stop.
This spinning attack uses your normal to hit modifiers and deals 2d12 plus damage modifiers (up from 2d6). You can't use extra attack with this feature nor use this feature as your extra attack. You can use this feature a number of times equal to double your proficiency bonus, resets on long rest.
  Keep a tally of the kills you make with this feature. We might upgrade it later.
  It is used in the Lost Mines of Phandelver and beyond campaign.