Dragon's Heart

You touch one willing creature and imbue it with the power to spew magical energy from its mouth, provided it has one. Choose acid, cold, fire, lightning, or poison. Until the spell ends, the creature can use an action to exhale energy of the chosen type in a 15-foot cone. Each creature in that area must make a Dexterity saving throw, taking 6d6 damage of the chosen type on a failed save, or half as much damage on a successful one. In addition, the creature who you affect with this spell gains resistance to the damage type of the breath weapon you gave it.