A bolt of icy frost streaks towards a creature you can see within range. Make a ranged spell attack against the target. On a hit, it takes 7d8 cold damage, and it must succeed on a Constitution saving throw or gain vulnerability to fire damage until the end of your next turn. 

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the damage increases by 1d8 for each slot level above 6th.