The threat posed by the White Walkers persisted throughout HBO's Game of Thrones.
Until Jon Snow and Daenerys Targaryen intervened, the Night King and his army of the dead advanced slowly toward the Seven Kingdoms.
Daenerys, as well as the audience, were unaware that she was carrying out a proverbial Targaryen prophecy.
A prophecy that, had Robert's Rebellion succeeded in exterminating every Targaryen, would have meant the end of Westeros and the entire world.
Aegon the Conqueror had a vision of the end of the world, according to the House of the Dragon spinoff's premiere. The Song of Ice and Fire was the name Aegon gave to his vision.
This is Game of Thrones' official name, and when it was said on screen, it had a significant impact on viewers.
Without Daenerys, the Long Night would probably have started, Westeros would have lost, and the Night King would have prevailed.