Valeska's Frost Cloud

You create a 20-foot-radius sphere of fog centered on a point within range. The sphere spreads around corners, and its area is heavily obscured. It lasts for the duration or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it.  Creatures in the spells area when it is cast, or when it enters the spell’s area or starts its turn there take 2d4 + Int mod points of Cold Damage (or half on a successful Dexterity Save).  Creatures in the spell's area have their speed decreased by 10 feet until the beginning of their next turn.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage of the spell increases by 2d4 points of damage for each slot level above 2nd.