Aside from being historically significant for the Starks specifically, the crypt is the site for many interactions that have been important to Game of Thrones' story. It's where we learn the popular version of Lyanna's death, told to us when Robert Baratheon and Ned visit her tomb. In the books, Jon, Bran, and Rickon all have dreams in which the crypt features prominently — it's a source of dread for Jon in particular. Before his death, Ned dreams of Lyanna's statue whispering to him, "Promise me, Ned," which we hear again in the season eight teaser. It's where Peytr recites the story of The Tourney at Harrenhal to Sansa after her return to Winterfell in season six and she finds the feather left by Robert. It's where Sansa and Arya have their private reunion in season seven, where Jon finally learns who his real parents are in season eight, and subsequently where he reveals the truth to his aunt, Daenerys, right before the Battle of Winterfell.
The crypt also serves a more practical importance in season eight. Not only is it huge and consists of multiple layers, but it also has various tunnels running through it to aid Northerners escaping from trouble. As soldiers prepare for the epic Battle of Winterfell, women, children, and elders are ushered into the crypt to hide in during the battle. In the second episode of season eight, Gilly instructs several people on how to enter the crypt, including a little girl who swears she'll protect everyone inside (poor, sweet summer child).
