Rust Monster's Gift

You have developed traits similar to those possessed by a rust monster, granting you the following benefits:

Rust Monster's Defense. You gain a +1 bonus to AC while you aren't wearing metal armor. However, your AC is decreased by 1 while you are wearing metal armor.

Corroding Touch. As an action, you can attempt to corrode a metal weapon, suit of armor, or shield. Choose a weapon or suit of armor that is made of metal and within your reach. If it is being worn or carried by a creature, the creature can make a Dexterity saving throw (DC 8 + your proficiency bonus + your Dexterity modifier) to avoid your touch.

If the object touched is either metal armor or a metal shield, it takes a permanent and cumulative −1 penalty to the AC it offers. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. If the object touched is a metal weapon, the weapon takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed.

You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.