Vestige of the Master of the Hidden Flame

A line of roaring flame 30 feet long and 15 feet wide emanates from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 7d8 fire damage on a failed save, or half as much damage on a successful one. Creatures within the center 5 ft. line have disadvantage on the saving throw.