Maul of Thunder

Weapon (warhammer), legendary

This oversized weapon can only be wielded by a Medium or larger character with at least 18 Strength, and medium creatures can only use it two-handed.

You gain a +3 bonus to attack and damage rolls when you use this weapon. When you use this weapon, you score a critical on a 19 or 20. When you score a critical with this weapon, it does an additional 1d8 thunder damage. A Huge or larger creature may use the Maul as a thrown weapon, in which case it returns to the hand of the thrower at the end of the thrower’s turn, unless the creature is unconscious or does not have a free hand, in which case it lands in the creature’s space.