Chilling Strike

A shard of ice forms in your hand, with which you can strike at one creature within range. Make a melee spell attack against the target. On a hit, the target takes 1d8 cold damage, and its speed is reduced by 10 feet until the start of your next turn. A creature can only suffer the movement reduction once.

At higher levels you can strike more often with the shard: two strikes at 5th level, three strikes at 11th level, and four strikes at 17th level. You can direct the attack at the same target or at different ones. Make a separate attack roll for each strike.