Doorbreaker
Weapon,
Rare
(requires attunement; cost 5000 gp)
Crafting Components
Adamantine hammer worth at least 2,000 gp
The head of this magic maul is shaped like an adamantine fist. You gain a +2 bonus to attack and damage rolls made with this weapon. When you hit an object or construct while wielding Doorbreaker, the hit is treated as a critical hit.
Doorbreaker has 3 charges. When you attack or touch a portal sealed with an arcane lock , you can expend 1 charge to cast knock on the portal. Doorbreaker regains 1d3 charges each dawn.
Source