Frost Bewreathed

You have become one with cold, and understand it well enough and are adapted to it well enough to live comfortably in otherwise hellish conditions to a standard mortal.

You have resistance to cold damage

You can live comfortably in temperatures as low as -180 degrees Celsius without suffering the effects of extreme cold

All attacks of yours that deal cold damage deal an additional cold damage for every ten degrees below freezing the temperature is currently

You can cast frostbite, ice knife, and ray of frost at will

You can innately call upon the power of deep winter, freezing temperatures and the hellscape they produce in order to, once per short rest, either cast cone of cold  or to cause all of your attacks to deal an additional 4d8s of cold damage for the next minute