BEWARE: This post contains spoilers for 'Game of Thrones' season 7.
Viserion, one of the three dragons magically hatched by Daenerys Targaryen in season one of HBO's Game of Thrones, has always occupied a background role compared with his more prominent brother Drogon (I'm using male pronouns because the dragons are named after men, but it's worth noting that dragons in the Game of Thrones universe have no fixed sex).
But now that he has died and been reborn as a zombie dragon, Viserion has busted out of the show's margins to become an epic closer. In the last scenes of this roller-coaster season, undead Viserion, mounted by the Night King, flies right on up to the Wall and slices it down in short order with his mysterious electric blue flame-breath. The towering icy barrier that has shielded Westeros from the predatory forces in the Land of Always Winter for thousands of years is breached, and the army of the dead pour through.
Ever since the Night King fatally skewered Viserion and revived his battered corpse in episode six, fans have wildly speculated about the zombified dragon's abilities. Some have predicted that he might become an ice dragon, a legendary monster alluded to in George RR Martin's A Song of Ice and Fire series, upon which Game of Thrones is based. In his point-of-view chapters, Jon Snow often reflects on tales he heard from Winterfell elder and storyteller extraordinaire Old Nan, who said these wintery beasts had breath so cold they freeze people solid in a heartbeat.
"These colossal beasts, many times larger than the dragons of Valyria, are said to be made of living ice, with eyes of pale blue crystal and vast translucent wings through which the moon and stars can be glimpsed as they wheel across the sky," wrote Martin in The World of Ice and Fire.
Undead Viserion does have the characteristic blue crystal eyes. But when the zombie dragon lets loose on the Wall, it is clearly with piping hot flames capable of searing through the ice. While the sapphire color of the fire matches Viserion's stylish new peepers, it is not consistent with the rumored frost-breath of an ice dragon.
So what in seven hells is Viserion breathing, and how will it affect his prowess in the wars to come? Perhaps we can find the answer in our own universe, bereft of dragons though it may be.
Some of the hottest flames harnessed by human engineering burn blue, such as oxyacetylene torches, which are used to weld and cut metal. The unusual color is sometimes derived from the chemical composition of the substance being combusted, but it's more often linked with increased oxygen flow to a flame.
Oxygen is highly flammable, making gas molecules within a flame much hotter and more excitable. That in turn generates a blue tint. Compared with standard yellow flames, which burn at around 1,000 °C (1,800 °F), the hottest blue flames can reach temperatures of 4,000 °C (9,000 °F) when fed by the extremely combustible substance dicyanoacetylene.
Perhaps in his resurrected wight form, Viserion gained some extra oxygenated dicyanoacetylene juice in his gullet that has shifted the composition, temperature, and hue of his flames.
This would seem to be in line with the final moments of the season finale, which depict the army of the dead walking through the rift Viserion has created in the Wall. If a normal dragon took a shot at taking down the structure with incandescent flames, we might expect to see rivers and pools flowing from the melting structure.
But it looks like Viserion completely vaporized the icy barrier, and the chunk that's missing appears to be floating off into the heavens as sublimated gas, instead of as liquid snowmelt. This may support the notion that Viserion's newly acquired blue flames could be several times hotter than his living brothers' fiery breath.
This is a huge deal when you think about it. It means that zombie Viserion and his Night King rider may be poised to deliver far more deadly blows than they will receive—from both warriors and dragons—in the final season. It also means that no matter who wins the war for Westeros, Viserion will always have a secure job as an industrial welder.
Of course, as other show-watchers have speculated, it could be that Viserion's blue fire has fantastical origins. As the series winds to a close, mystical powers are becoming more prominent, and the undead dragon's ability may be chalked up to the waxing power of magic in Westeros.
Either way, brace yourselves: Dragon brawls are coming.
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