Ice dragons have come to Westeros and they're not here to make friends. The White Walkers have killed and resurrected Viserion. His eyes are now an icy blue and instead of fighting for Daenerys, Viserion fights for the White Walkers. Is this new Viserion just an undead version of the same dragon we've seen since Season 1, or will he have a new set of icy powers to match the army of the dead? What can ice dragons even do on Game of Thrones?
Now that Jon Snow's enemies have the most powerful weapon known to man — an undead dragon, things are likely to get even worse for our heroes. In addition to an ever-growing army of the dead that includes wight horses and zombies and the fact that they can only be killed by Valryian Steel, having an ice dragon is just the icing on the Night King's death cake. With an ice dragon under their control, what new methods of destruction will the Night King use to claim Westeros?
There is some precedence for ice dragons in the A Song Of Ice And Fire Books, but only in rumors and legends. Those ancient stories never talked about undead dragons, though, so fans may be seeing something entirely different. To figure out what Viserion's abilities are, it needs to be determined if he truly is an ice dragon or is simply undead.
Ice Dragons haven't been prominently featured in Game of Thrones, but the books allude to their existence multiple times. As described in the book The World of Ice and Fire, ice dragons "are many times larger than [normal dragons,] are said to be made of living ice, with eyes of pale blue crystal and vast translucent wings." While Viserion doesn't seem to be made of living ice or have translucent wings, there's no denying that his eyes are now an icy shade of blue.
The World of Ice and Fire goes on to describe the defining ability of ice dragons. "Whereas common dragons (if any dragon can truly be said to be common) breathe flame, ice dragons supposedly breathe cold, a chill so terrible that it can freeze a man solid in half a heartbeat." Wight Viserion has yet to be seen in action, but the final say on whether or not Viserion is an ice dragon will come down to what comes out of his undead mouth.
It should be mentioned that while The World Of Ice And Fire features the most matter-of-fact description of ice dragons in the SOIAF series, it also doubts their existence. As the book explains that "as ice dragons supposedly melt when slain, no actual proof of their existence has ever been found." If Viserion starts breathing fire instead of ice, it's likely that there will not be an ice dragon at all on Game of Thrones. However, that doesn't mean that Jon Snow and Dany's war against the undead is going to be any easier. Whether it breaths fire or ice, a dragon is still a dragon — and you don't want to be on its bad side.