Aurora Stream

A ribboning stream made up of glowing strands of ethereal iridescent lights rushes through an area you choose within range. The area of the stream  consists of up to 3 10-foot cubes, which you can arrange as you wish. Each of these cubes must have at least one face adjacent to the face of another cube. Every creature in the area must make a Dexterity saving throw: it takes 8d6 Radiant damage on a failed save, or half as much damage on a successful one.

When cast at a level above 3rd, for each spell slot expended above 3rd level, the spell creates an additional cube.