As two actions, you teleport entire chunks of the earth or stone 10 meters into the air, where they fall onto the targets below at a point within 20 meters. Each creature in a sphere centered on that point must make a Reflex saving throw. A target takes 7d6 bludgeoning damage on a failed save, or half as much damage on a successful one.
In addition, the ground in the affected area becomes difficult terrain until cleared. Each 1-meter square portion of the area requires at least 1 minute to clear by hand.
You can increase the damage by 2d6 for each additional mana or psi expended.