Descent (Patreon)

Weapon (war pick), very rare

A metal pick with a crimson plume, representing the diligent woodpecker. You gain a +2 bonus to attack and damage rolls made with this magic weapon. This weapon deals double damage to creatures made of wood as well as wooden objects and structures. 

Drum. When you hit a creature with a melee weapon attack with this weapon, all subsequent melee attacks made with this weapon against the same creature deal an additional 1d4 piercing damage. This extra damage continues to increase this way until you miss a melee attack with this weapon, you attack another target, or a turn passes without having damaged a creature with this weapon. 

If hitting them doesn't work, you didn't hit them enough.