Chromatic Storm

You create a storm of energy in a 20 ft. radius Sphere centered on a point you can see within range. 

Choose Acid, Cold, Fire, Lightning, Poison, or Thunder for the type of storm you create. Each creature in the storm must make a Constitution saving throw, taking 5d8 damage of the chosen type on a failure, or half as much damage on a success. A creature makes this saving throw if it enters the Sphere for the first time on it's turn, or ends it's turn there. A creature can take this damage only once per turn.

On subsequent turns, you can take a Magic action to move the Sphere up to 30 ft.

Using a Higher-Level Spell Slot. The damage increases by 1d8 per level of spell slot above 4.