Thorvald’s Thunder Punch

You charge your fist with thunderous energy. Make a melee spell attack, on a hit, the target suffers 3d8 thunder damage and must succeed on a strength saving throw or be knocked back 5ft. and knocked prone.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd.