Corpse Explosion

Detonate a pile of bones or the corpse of a Medium or Small creature within range. Each creature in a 10-foot radius sphere centered on the target must make a Dexterity saving throw, taking 2d8 necrotic damage on a failed save or half as much damage on a successful one. When an undead under your control dies, you can immediately cast this spell targeting it. When cast in this way, the casting time is reduced to 1 reaction.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d8 for each slot above 1st.