After surviving the arctic you have learned to channel the power of it.

Arctic Resilience

You have endured the cold and have grown resistant to it and can not be frozen or have your speed reduced by the cold. In addition you gain proficiency in survival and have advantage on survival checks in cold climates. Tundra, Mountain etc

Arctic Blade

You engrave one weapon with a rune of cold, once per turn when you hit an attack you can deal 1d4 extra cold damage. (2d4 damage on a crit) In addition you can imbue your weapon with overwhelming power 2 times per long rest as a bonus action. When you activate it your extra cold damage does 1d8+strength modifier, this effect lasts for 2 turns.

Improved Rune

Your rune becomes even stronger and you can now engrave another weapon with it. Your extra damage becomes 1d6 damage and your freezing surge becomes 1d10 damage.

Arctic Expertise

You gain immunity to the cold and expertise in survival checks and one other skill of your choice.

Expertise

You gain 1 expertise of your choice

Rune Mastery

You have mastered the cold and your extra cold damage does 1d8 damage now and your arctic surge does 1d12 damage now.