In A Song of Ice and Fire, the series of books that inspired the TV version of Game of Thrones, there is a popular myth surrounding a hero figure named Azor Ahai. According to a legend whose origins are rooted in the religion that Melisandre practices, the White Walkers swept across the world long, long ago, leaving death and destruction in their wake. Azor Ahai allegedly rose up to save the world from eternal night by forging a legendary sword — Lightbringer — that helped him push the Others far, far into the North, where they were all but forgotten about.
In A Dance With Dragons, the prophecy about Azor Ahai is stated as follows: "When the red star bleeds and the darkness gathers, Azor Ahai shall be born again amidst smoke and salt to wake dragons out of stone." Seeing as the White Walkers are back and more terrifying than ever, it stands to reason that Azor Ahai's reincarnation is, too.
