Hexaxe

This handaxe amplifies curses bestowed on its enemies. The weapon has 3 charges and regains all expended charges daily at dusk. While you’re holding the axe and are forced to make a Constitution saving throw to maintain concentration on a warlock spell, you can use your reaction to expend 1 of the axe’s charges to add your Charisma modifier to the total of the saving throw.

You gain a +1 bonus to attack and damage rolls made with this magic weapon against creatures under the effects of a warlock spell you cast that requires concentration.