Beget Boulder

You infuse a handful of pebbles with powerful transmutation magic. For the duration of the spell, you can throw one pebble as an attack action that provokes attacks of opportunity. Shortly after the pebble leaves your hand, its size and the force of the throw increases dramatically as the pebble expands into a massive boulder. Each boulder deals 6d6 bludgeoning damage on a failed save and half as much on a successful one. The boulders deal double damage against structures and objects.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.