Enfeebling Adamantine Fragmentation

You throw a small sphere of magical adamantine at a point up to 150 feet away, which explodes on impact, launching tiny adamantine needles and elemental bursts in every direction. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 piercing damage and gains vulnerability to one of the following damage types 1 fire, 2 cold, 3 lightning, or 4 acid on a failed save (your DM may allow you to choose or make you roll to determine the vulnerability type, or half as much damage and does not gain vulnerability on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 3rd.