Bubble Cutter

You throw a set of pebbles that turn into high speed spinning bubbles. They continue until stopped by a solid object, creature, or until they reach the end of their range. If the bubbles would strike a creature, that creature must make a Strength saving throw. On a failed save, the bubbles all collide with the target and stop, dealing half damage. When the object strikes something, the object and what it strikes each take 3d12 force damage. For every subsequent creature the bubbles hit, they take 1d12 less force damage, to a minimum of 1d12. 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d10, for each slot level above 2nd.