It's the exquisitely-drawn villains that have elevated Game of Thrones above lesser swords and sorcery sagas. Lord of the Rings had its huge fiery eye-ball wobbling apoplectically from the Dark Tower; Harry Potter gave us Ralph Fiennes sulking beneath his Voldemort prosthetics. But neither could hold a flaming broadsword to the Westeros tag-team of depraved Justin Bieber tribute act Joffrey (Jack Gleeson) and torture-porn-boxset-in-human-form, Ramsay Bolton (Iwan Rheon).
Beheadings, infanticide and bad monologues were all in an afternoon's work for the bad-boys of the Seven Kingdoms. And how we cheered as each received his (spectacularly horrific) comeuppance. Yet if their agonising deaths – by poison and peckish pooch respectively – were entirely merited, the duo's absence has left Game of Thrones with an ominous bad guy deficiency. Cersei's love for her children has humanised her too much for us to loathe her; newcomer Euron Greyjoy (Pilou Asbæk) is a two dimensional 1980s action movie nasty parachuted in at the last moment. Hating the Iron Born bonehead feels like a waste of effort.
So what about the Night King (Vladimír Furdík), you may ask? Well yes, the looming conflict between Jon Snow (Kit Harrington) and the White Walker leader should be Game of Thrones's most epic to date. The difficulty is that the Night King is more grimacing metaphor than plausible antagonist. Sweeping down from the north with his deathless hordes, he embodies the destructive inevitably of time and of the seasons. Winter is coming and there's little humanity can do to forestall this grim inevitability.
Early on, when GoT show-runners David Benioff and DB Weiss were tracking George RR Martin's source material more or less faithfully, the Night King was a shadowy presence. The problems with the character only manifested in earnest as the show deviated from the books. In the novels, the Night King is an ancient myth: no more likely to intervene in present day Westeros than Bran the Builder, creator of the Wall.
Benioff and Weiss's misstep was to promote the zombie-lord to the first rank of villains. With just one season left after next week's finale and Ramsay and Joffrey long gone, he has, by default, become the show's ultimate nemesis. Alas, the more we see of the Night King, the less interesting he is. In Lord of the Rings, Sauron was kept entirely off stage (even in Peter Jackson's tin-eared movies he was confined to the occasional fiery cameo). Game of Thrones has, by contrast, given us the Walker kingpin's entire life story, via flashbacks from Bran (Isaac Hempstead Wright). And in the process it has thoroughly demolished his mystique.
So we know he was originally one of the First Men to colonise Westeros and was sacrificed by the Children of the Forest, who tied him to a tree and pressed the magical dragonglass into his chest. However, the Children’s plan to create an army to repel the First Men went horribly awry and the Night King became patient zero of the Walker plague: a destructive force whose only instinct is to bring frosty ruin upon all living things.
Admittedly, no other Game of Thrones regular has had so dramatic an entrance as the Night King. In the season five episode Hardhome, he emerged from the ranks of Walkers and Wights and tauntingly eye-balled Jon Snow while resurrecting dozens of recently-slain dead Wildlings as glacial ghouls (it wasn't the first time he had appeared - but this was when his importance to the series was confirmed). Your blood froze even as your pulse raced.
Sadly, it's been downhill ever since. (Spoilers ahead.) The Night King has spent the intervening two years mooching around north of the Wall with his minions. His recent face-off against Snow's rag-tag band of brothers (chronicled in the latest, widely leaked episode) promised much yet was ultimately a triumph of sound, fury and CGI over the Machiavellian suspense that was once Game of Thrones's winning attribute.
Joffrey and Ramsay were fan favourites when they were on screen. But it's only now, as GoT scrambles to fill the void left in their wake, that viewers will have come to truly appreciate the importance of a good villain. Without one, GoT is in danger of becoming just another fantasy romp.
