Boon of Tundra (TTR)

You have immunity to cold damage. If you would take cold damage, you instead gain the effects of a 4th level Armor of Agathys. You can also cast 9th Level Ice Knife (save DC 20, or yours whichever is higher) at will, without using a spell slot or any components. You can cast this against up to 3 Targets. This spell cannot be countered, and works in antimagic areas. You are unaffected by any obscurity or movement penalties caused by Snow or Blizzards.