Lingering Breath

You gain the ability to choose to cause your breath weapon to form a lingering cloud whenever you use it.

Whenever you use your breath weapon, you can choose to reduce the amount of damage it deals by one hit dice. If you do, the breath weapon then lingers asa cloud of magical energy that lasts for 1 round. The could occupies a space in a 10-foot radius sphere that is a distance away from you that is equal to the length of your breath weapon.   Until the duration ends, any target that ends its turn within the area of the cloud must make a Constitution saving throw against your Breath Weapon Save DC, taking the amount of damage your breath weapon normally deals, but minus one hit dice on a failure, or half as much on a success.