Ubtao's Tiny Teraform

You touch the ground beneath you and ask Ubtao, god of creation, to cause it to vibrate. Each creature in a 20ft cube below the ground's surface must make a Dexterity save. A creature takes 4d6 bludgeoning damage and has its movement speed halved until the end of its next turn on a failed save, or half as much on a pass.

You briefly learn each creature's location that takes damage from the spell.

At Higher Level. When you cast this spell using a slot of 3rd or higher, the damage increases by 1d6 for each slot above 2nd.