Darwin’s Acidic Horror

You spin a tale of acid creatures rising up and striking every creature in a 30-foot cube centered on a point you choose within range so realistic it summons them. Each creature in that area must make a Charisma saving throw. Plants and oozes aren’t affected, and humanoids and dragons make this saving throw with disadvantage. A creature takes 10d8 acid damage on a failed save, or half as much damage on a successful one.