Decompose Corpse

You target a corpse you can see or an undead. If a corpse it decays into dust and ash. A corpse decayed this way cannot be regenerated or be the target of any resurrection spells, only Wish or Miracle can restore the body.

For the undead, they make a CON save. On a failure they are instantly destroyed and turned to dust if they are CR 4 or lower, otherwise they take 2d12 force damage. On a success there is no effect.