Lodestone Caltrops

This small gray pouch appears empty, though it weighs 3 pounds. Reaching inside the bag reveals dozens of small, metal balls. As an action, you can upend the bag and spread the metal balls to cover a square area that is 5 feet on a side. Any creature that enters the area while wearing metal armor or carrying at least one metal item must succeed on a DC 13 Strength saving throw or stop moving this turn. A creature that starts its turn in the area must succeed on a DC 13 Strength saving throw to leave the area. Alternatively, a creature in the area can drop or remove whatever metal items are on it and leave the area without needing to make a saving throw. The metal balls remain for 1 minute. Once the bag's contents have been emptied three times, the bag can't be used again until the next dawn.