Festerwood Masher
This festerwood hammer has amber pustules on its end that have enriched the wood with its corrosive properties. You gain a +2 bonus to attack and damage rolls made with this magic weapon.
In addition, this hammer has 3 charges and regains all expended charges daily at dusk. When you hit a creature or object with the hammer, you can expend 1 of its charges to magically release some of the corrosive acid. When you do, if the target is Large or smaller, that target takes a cumulative −1 penalty to its AC that lasts for 1 minute. If the target is Huge or Gargantuan, it takes this penalty after you expend either 2 or 3 charges in this way, respectively. This hammer deals an extra 1d4 acid damage to any target it hits for each −1 penalty to AC it has in this way.
The knight's once shining armor was now pockmarked by acid; the leather straps holding it together snapped one by one. The raucous spectators roared approvingly as the champion fell to his knees. "What foul magic cursed that cudgel?" the knight gasped with his remaining breath. "Curse? It's the blessing of the Festerwood, and it won't be denied."