Voice of The Dragon

Your earth-shaking shout awakens the soul of the fallen dragon, Erothius, to imbue his wrath into your weapon. Once per long rest, you may shout "Nos Al Kron" at the top of your voice as a bonus action. If you do so, your next attack will be a guaranteed critical hit. If you use a melee weapon, you reach with a cone shape with a range of 30ft instead of your base range. If you use a range weapon, the ammo that you shoot explodes violently into a 30ft sphere of pale green mist upon contact, dealing the same amount of damage as you rolled on your damage die. After the critical hit, you roll with disadvantage on all of your other hit rolls until you have a long rest.