Elemental Onslaught

You blast elemental energy from your fingertips in a line 90ft in length, 5ft in width. All creatures in the line must make a dexterity saving throw, on a fail they take full damage, and a success they take half damage and don't suffer any additional affects. Choose an elemental based on the escense you used to cast the spell, all targets take 4d6 damage based on the elemental chosen. 

Earth - Creatures take 4d6 bludgeoning damage and are knocked prone as you blast them with Earth energy.

Water - Creatures take 4d6 cold damage and are petrified in ice until the start of your nect turn as they are blasted with Water energy.

Fire - Creatures take 4d6 fire damage, and take 2d6 fire damage on the start of each of their turns until they put out the flames as they are blasted with a line of fire.

Air - Creatures take 4d6 lightning damage and are stunned until the start of your next turn as you blast them with air enegy.

Upcasting:  For every extra level you cast the spell at they take an additional 1d6 damage, this applies to the extra fire as well. For every two levels you upcast at you can choose one of two additions. 1) Choose an additional elemental and apply it's damage and abilities on top of previously chosen options. 2) Choose a secondary affect, that affect lasts two turns longer, for Earth and Fire they can't stand up or put out the fire for the duration.