Aleksi's Dragoon Lance

A spark of light builds in your pointing finger. When the spell ends, either because the casting is complete or because you decide to end concentration early, the light blossoms with a low roar into an explosion of energy that shoots forward in a 150 feet long and 5 feet wide line that you choose. Choose acid, cold, fire, lightning, poison, force, radiant, psychic, thunder, or necrotic for the type of damage you create. Each creature in the line must make a Dexterity saving throw. A creature takes damage equal to the total accumulated damage type on a failed save, or half as much damage on a successful one. When cast this spells damage begins at 4d6, at the beginning of your next turn, if you still hold concentration, the spells damage is increased by 6d6 to a total of 10d6.