Annam's Anvil

When attuned to this weapon, the wielder gains a +3 to attack and damage rolls made with the weapon, and it deals double damage against structures and objects. 

When attuned to this weapon, the wielder may expend one charge as a bonus action to activate Annam's Anvil for 1 minute. When activated, the Maul scores a critical hit on a 19 or a 20 on the dice roll, it gains the thrown property (30/60) once thrown the maul will return to the user, and it does an additional 1d6 magical bludgeoning damage, and an additional 2d10 damage determined by chance. Roll a d4, the outcome determines the damage type. (1-Fire, 2-Lightning, 3-Thunder, 4-Cold).

Likewise, when an attack with the activated weapon hits a creature, they must make a Wisdom Saving throw (DC = 8 +Proficiency Bonus + Int Modifier) or be stunned until the end of their next turn

Proficiency with a Maul allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Damage: Fire, Stunned, Expend one charge as part of a weapon attack, creatures within 10 feet of you are knocked in a random direction 10 feet away from you; expend one charge to use Earth Glide ability for 1 minute; expend 2 charges to deal an additional 2d6 bludgeoning damage per melee attack, the target must succeed a Wisdom saving throw DC 16 or be stunned until the end of their next turn, this effect lasts for 1 minute., Requirement of Str 22 to wield if not a large creature, Heavy, Two-Handed, Topple