Festerwood Masher (Patreon)

Weapon (a maul or warhammer), very rare (requires attunement)

This heavy festerwood hammer has amber pustules on its end that have enriched the wood with corrosive properties. You gain a +1 bonus to attack and damage rolls made with this magic weapon. In addition, this hammer has 3 charges that can be used when striking a target. When you hit a target with the hammer, you can choose to expend 1 charge to magically release some of the corrosive acid stored within the wood. 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. A Huge or Gargantuan target takes this penalty only after you've expended either 2 or 3 charges in this way, respectively. Targets take an extra 1d4 acid damage for each -1 penalty to AC they have in this way each time they're hit by the hammer. The hammer regains all expended charges each day at dusk.

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."