My drawing and simple explanation for season 5 episode 8 from game of thrones.
Spoilers follow for the eighth episode of the fifth season of Game of Thrones
The harrowing 15-minute battle sequence that ended "Hardhome" — featuring Jon Snow and the wildlings trying to escape a sudden attack by the White Walkers — occurs nowhere in George R. R. Martin’s book series.
The biggest change is an obvious one — the huge, special effects–heavy battle scene featuring rampaging skeletons, massacred wildlings, and Jon Snow fighting a White Walker is entirely new to book readers. Indeed, in the five volumes published so far, Jon hasn't yet fought or even seen a White Walker.
In the battle, the unstoppable undead horde massacres human after human, and despite Jon killing his White Walker opponent, the human survivors end up merely fleeing rather than winning. This tone actually quite resembles a book sequence early in the third book, A Storm of Swords, when undead hordes rout the Night's Watch's ranging party at the Fist of the First Men.
The show rather botched its adaptation of that sequence, showing the approaching White Walker army at the end of season two, and then cutting ahead to the underwhelming aftermath in the first scene of season three, apparently for budget reasons. Now, the series is making up for it.
Benioff and Weiss, instead, have been trying to show they haven't forgotten about the White Walkers. Back in season two, they invented a scene in which Jon Snow sees a White Walker taking away Craster's son. Then, in season four, they invented a scene showing a Walker taking another of Craster's sons and changing its eyes to blue. This was all heavily implied to be going on in the books, but not directly shown.
That scene last year revealed another tantalizing tidbit — that the White Walkers appear to have a leader with a horned crown. And some HBO supplementary material revealed that leader's name — the Night's King.
We also learn another way the White Walkers can be killed, in addition to dragonglass. Jon's Valyrian steel weapon kills his Walker opponent, rather than shattering on contact as other weapons have. This has been set up in the books, but we haven't seen it in action. (Early in the fourth book, A Feast for Crows, Sam reads in an old book that a mythical hero killed others with a blade of "dragonsteel," and he and Jon speculate that that could refer to Valyrian steel.)
Of course, some elements of the Walkers' attack appear to be show-only inventions. The fast-moving skeletons, for instance, don't appear in the books — the corpses the Others reanimate have flesh on them and are slow-moving. These skeleton troops, introduced in the season four finale, were the idea of director Alex Graves, so they're likely not an adaptation of Martin's future plans.