Ever since Bran Stark returned to Winterfell as the Three-Eyed Raven, he's been spending a good amount of time in the godswood around a strange weirwood tree. As it turns out, those trees have some wild history. They are deeply magical, with some even bearing carvings of faces, which were supposedly created by the Children of the Forest, who allied with the First Men thousands of years ago when the White Walkers first attempted to invade the continent. The specific tree where Bran spends time is the exact tree that guarded its cave even from the Night King himself. Although it's never been said outright, it seems that something about the weirwood tree has power against the White Walkers, which could definitely come in handy soon.
