As two actions, a glowing 30-centimeter diameter ball of emerald acid flashes from your hand to a point within 20 meters and then blossoms into an explosion of acid. The acid spreads around corners. Each creature in a sphere centered on that point must make a Reflex saving throw.
On a failure, it takes 4d8 acid damage immediately and additional acid damage equal to half the amount of acid damage dealt at the end of its next turn and its armor or natural armor is corroded 1 until the end of your next turn.
On a critical failure, it takes twice as much damage and its armor or natural armor is corroded 2 until the end of your next turn.
On a success, it takes half as much damage.
On a critical success, it takes no damage.
You can increase the damage by 1d8 for each additional mana expended.
Delay Blast. You can expend 1 additional mana so the ball lingers at the point of origin while you concentrate on the spell for up to 1 minute. If at the end of your turn the ball has not yet detonated, you can increase the damage by 1d4. When the spell ends, either because your concentration is broken or because you decide to end it, the ball explodes.