Discombobulate!

You slap the ears of your target while yelling “DISCOMBOBULATE!”

When casting, you must strike both ears of the target simultaneously. The target must make a Constitution saving throw when struck, and does so for every turn of theirs. On a fail, they are prone and have disadvantage on everything and cannot stand up for a period of 2 rounds. When cast, they take 2d4 thunder damage instantly. 

At higher levels

At 5th level, the prone duration increases to become 4 rounds.

At 11th level, you can cast this Cantrip as a reaction.

At 17th level, you now deal 2d12 thunder damage.