Swirling Wind

You summon a 10 foot tall 10 foot wide cylinder of swirling wind. If a creature enters the cylinder or starts it’s turn there the following effects happen  

The target has to succeed a strength saving throw equal to your spell save DC or be knocked prone and take 2d10 damage or half as much on a successful save. The target can use half it’s movement to repeat the saving throw and get up from prone.