Evocation 7. Casting it requires 41 and consumes 3. It is a battlefield enchantment.is a generic combat spell available at
Acid storm hits approximately 5% of the battlefield each turn with 4 armor piercing acid damage every round until the caster dies, leaves the battlefield, or the battle is over. The acid damage can cause rusting of iron armour and weapons, which provides a chance of them breaking when damaged.