Boreal Wave

You conjure up a wave of electrically charged, luminous energy that takes the form of an aurora and crashes down on an area within range. The area can be up to 30 feet long, up to 10 feet wide, and up to 10 feet tall. Each creature in that area must make a Dexterity saving throw. On a failed save, a creature takes 2d8 cold damage and 2d8 lightning damage and is knocked prone. On a successful save, a creature takes half as much damage and isn’t knocked prone. The aurora then spreads out across the ground in all directions, illuminating its area and within 30 feet of it for one round with dim light, and then it vanishes.