As two actions, you create a rain of thorns at a point within 20 meters. Each creature in a cylinder centered on that point must make a Reflex saving throw.
On a failure, it takes 7d6 damage.
On a critical failure, it takes twice as much damage.
On a success, it takes half as much damage.
On a critical success, it takes no damage.
You can increase the damage by 2d6 for each additional mana expended.