When the northern outpost of Polarmino is cut off from the rest of Equestria by an unnaturally vicious snowstorm, the Council sends Sky Streak to investigate. However, what he finds there will force him to confront an entire civilization of Equestria's most ancient foes. But even with a bag of tricks and a new ally, Sky may not be prepared for the greatest danger of all, which threatens not only his life, but the existence of all of Equestria.