Bluster

A loud, swirling breeze 40 feet long and 5 feet wide blasts from you in a direction you choose. A creature in the line must make a Strength saving throw. A creature takes 1d10 thunder damage and is knocked prone on a failed save, and half as much damage and isn't knocked prone on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d10 for each slot level above the 1st.