Mountain Pass. Make your way to the red and black  on the map. From this tile there some guy inside a cabin who tends to throw pipe bombs at passerbys. Meaning, don't hang around for too long. Head west/northwest, then down.
This mutation grants:
+8-10 cold resistance +Immunity to the cold effect.
Takes up a soak slot.
His/Her/Its skin is thick and dusted with white fur.