Tyron's Mighty slam

You concentrate your magical energy to channel the magic of the dragon lord Tyron. In a space you can see within range you create a antigravitational force in a 30ft radius cylinder that lifts creatures 20ft of the ground and slams them down immediatly afterwards. Every creature in range must succeed on a Strength saving throw or take 5D6 bludgeoning damage and be knocked prone. On a succesful save the creatures take half damage and are not knocked prone.

Creatures in the large category and above make the saving throw with advantage. 

When you cast this spell with a higher level spell slot the damage increases by 1D6