Borealis' Mist

Your mouth becomes a gaping maw, filled with jagged teeth and the power to unleash a blast of freezing air. You exhale a 30-foot cone of ice, each creature in the area must make a Dexterity saving throw or take 5d6 cold damage and have their speed halved until the end of their next turn.
After the attack, you immediately revert back to your normal form. If you transformed while in mid-air, you will fall and take fall damage if you land more than 20 feet from the ground.