Copper Dragonborn Breath Weapon

You can instead of your normal breath weapon, you exhale gas in a 15-foot cone. Each creature in that area must succeed on a Constitution saving throw. On a failed save, the creature can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the creature can use either an action or a bonus action on its turn, but not both. These effects last for equal to your constitution modifier in rounds (min of 1). A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus.