As two actions, a sphere of crushing force forms at a point within 20 meters. The gravity spreads around corners. Each creature in a sphere centered on that point must make a Reflex saving throw.
On a failure, it takes 4d8 concussion damage, is slowed 1 until the end of its next turn, and is pulled 3 meters toward the center of the area if it is Medium or smaller.
On a critical failure, it takes twice as much damage, is slowed 2 until the end of its next turn, and is pulled 6 meters toward the center of the area if it is Medium or smaller.
On a success, it takes half as much damage.
On a critical success, it takes no damage.
You can increase the damage by 1d8 and affect a creature of a larger size for each additional mana expended.