conjure ice harpoons

you dip your fingers in water and make a slashing motion conjuring 4 harpoons made of magic ice on hit the enemy has to make a strength save or be pinned to the ground doing 2d6 cold and 1d6 cold and will need to make a successful strength save to get out of prone and gain movement the saving throw is the creatures action 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, you gain 2 more harpoons per level