Chilblain Strike

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects and then is overwhelmed with intense cold until the start of your next turn.  The target takes and additional 1d4 cold damage and has its speed reduced by 10 feet until the start of your next turn.

This spell's damage increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).