If there's one thing to take away from last night's episode of Game of Thrones, it's that....(spoilers ahead!)
...even in death, Daenerys' older brother Viserys continues to be an incredibly huge pain in her arse.
Though the show's never spent too much time fleshing out the personalities of Daenerys' two smaller dragons, Rhaegal and Viserion, last night we saw that at least in that particular way, Viserion takes after the deceased uncle he's named for. In a moment of crisis when Daenerys needed help the most, Viserion managed to get himself slain by the Night King who, as fate would have it, is an excellent javelin thrower in addition to being a nightmarish ice demon. In a terrifying callback to "The Spoils of War," where we saw Drogon struck with a massive arrow shot from a huge crossbow, Viserion falls victim to the Night King, who manages to take him down with a single ice spear, causing him to fall into a frozen lake and die.
After Daenerys, Jon, and the rest of the men who'd left in search of a wight head back to the Wall, we see that the White Walkers have dredged Viserion's body out of the lake and turned him into a wight. (Go on and have a Yu-Gi-Oh chuckle, you've earned it.)
Obviously, Viserion's resurrection raises a number of important questions about just what the hell it all means. For starters, what is Viserion now?
As far as we know right now, Viserion isn't exactly an "ice dragon" in the way a lot of folks (myself included) immediately assumed when we first saw his newly-ice blue eye open up last night. Rather, he's a wight like any other living thing that the White Walkers kill and reanimate. The distinction might not seem like an important one, considering that a wight dragon probably would have some form of fire breath, but it's worth making considering that George R.R. Martin's already written explicitly about ice dragons before and that's not quite what Viserion is.
"The road beneath the Wall was as dark and cold as the belly of an ice dragon and as twisty as a serpent." - Jon's 8th chapter, A Dance with Dragons
Martin's The Ice Dragon is a children's book set in another magical world separate from that of A Song of Ice and Fire, in which a young girl befriends a feared and misunderstood ice dragon who's a harbinger of winter. There, the ice dragon is a naturally occurring creature who lives contemporaneously with fire-breathing dragons. This ice dragon lives a life of its own, seemingly without any interaction with anyone even vaguely resembling the White Walkers, and it's able to think for itself.
If Viserion's anything like the bears and horses the White Walkers have killed, however, then he's become more of a living weapon than a thinking, feeling being — and could be vulnerable to all the same things other wights are, like fire and dragonglass. There's a chance that a wight dragon might have some sort of resistance against fire, but George R. R. Martin's novels are very, very cagey about the natural of dragon's magic.
"The snowfall was light today, a thin scattering of flakes dancing in the air, but the wind was blowing in from the east along the Wall, cold as the breath of the ice dragon in the tales Old Nan used to tell." - Jon's 10th chapter, A Dance with Dragons
Stories of ice dragons do exist within A Song of Ice and Fire, but it's never made clear how much of that lore is simply a myth drawn from long-forgotten facts that have become fantastical over time. Jon Snow makes mention of stories that Old Nan once told him as a child about ice dragons, and multiple people reference the ice dragon constellation that features something like a North Star.
When Game of Thrones first began, we could scarcely imagine that by the seventh season, we'd see men with flaming swords fighting undead demon polar bears, but time makes fools of us all. Everything about this season has been equal parts agonizing and wonderful — as is often the case with slow burns that finally begin to pay off — and that's particularly true of this undead dragon business. We always hoped that this story would close out on a ridiculously epic note, and that was never going to be possible unless there was something that could challenge Daenerys and her dragons.
The Night King's new pet is the most logical solution to balancing out the power dynamics leading up Game of Thrones' finale and, as annoying as it is, we're at a point now in the series where there are no rules about how the magic works. That creepy arse dragon could be just as vulnerable to obsidian as its new, undead family members, or it might only fall victim to the fire of another living dragon. Only time will tell.