Conjure Caltrops

You create a set of caltrops (as described in the PHB, pg.15) in a free hand of yours. You can deploy the caltrops as part of the action used to cast this spell. 

The caltrops disappear when the spell ends. creating a new set of caltrops with this spell causes any old sets to disappear early. 

Damage dealt by caltrops created this way is considered magical.

The damage of the caltrops, created increases by 1D4 when you reach 5th, 11th, and 17th level