Ash to Winter / Winter to Ash

A twin spiral of frost and flame springs forth from you, converging on a point of your choice within range. Each creature in a 15-foot-radius sphere centered on that point must make a Constitution or Dexterity saving throw, dependent on primary damage typing.

Ash to Winter: All creatures in range must make a Constitution saving throw, take 3d6 fire damage and 3d6 cold (primary) damage on a failed save, and suffer one level of exhaustion (Maximum level of exhaustion that can be given from this spell is 1). On a successful save damage is halved and no additional effect occurs

Winter to Ash: All creatures in range must make a Dexterity saving throw, take 3d6 cold damage and 3d6 fire (primary) damage on a failed save. On a successful save damage is halved. For the next 1 minute the terrain within the cast area becomes unstable and slippery. All creatures moving through on the ground must make a Dexterity save, and on a fail, fall prone.

 At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage of the primary type increases by 1d6 for each slot level above 3rd.