You release a stream of fire from your hands, targeting a line that is 30 feet long and 10 feet wide, filling it with a continual stream of fire. Any creature that is in the area when you cast the spell or enters the area before the start of your next turn must make a Dexterity saving throw, taking 4d6 fire damage on a failure, or half as much on a success. On each subsequent turn for the duration, you can use your action to release a new line of fire with the same effect.