Caustic Bones

You cause an alchemical reaction in an undead under your control. Corrosive crystals grow on its body for the duration of the spell. When the affected undead dies, the crystals burst into shards in every direction. All creatures in a 10ft radius must make a Dexterity saving throw, taking 1d10 acid damage on a failed save, and half as much damage on a successful one. 

At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, you can target an additional undead for each slot level above the first.