Blessed are the dead
Weapon (warhammer), rare(requires attunement)
The weapon can hold one charge. As a bonus action, the attuned character can expand one charge to reroll any 20-sided die. This decision must be taken before knowing if the roll is successful.
To recharge the weapon, the attuned character must willingly fail a roll of a 20-sided die. That roll cannot be a skill roll.
This weapon changes its appearance everyday, but always acts as a regular warhammer.