Corrosive Wave

You call forth a deluge of acid that falls forth like a tidal wave, dousing your enemies in a corrosive substance that eats away at their bodies. Choose a point you can see within 30 feet- all creatures in a 20-foot long, 10-foot wide rectangle centered on that space must make a Dexterity saving throw or be hit by the acidic wave, taking 4d6 acid damage. In addition, creatures who fail the save take 2d6 acid damage at the start of their next turn, and until the end of your next turn, have their movement speed halved and disadvantage on Dexterity saving throws. On a successful save, the creature takes half damage from the initial impact and suffers no additional effects.

At Higher Levels: When you cast this spell with a slot of 4th level or higher, the initial and secondary damage increases by 1d6 for each slot level higher than 3rd.