Is It Possible to Kill a Dragon on Game of Thrones? Yes, but It's Not Easy
Of all those vying for the crown on Game of Thrones, Daenerys Targaryen seems to be the front runner. Despite a crushing blow from Euron Greyjoy, she's still got the Unsullied army in her ranks, a handful of major allies, and a gang of motherf*ckin' dragons. Since these winged badasses are Dany's strongest asset when it comes to taking down the Lannisters (and conquering Westeros as a whole), it makes sense that her greatest enemies want to destroy them. In "Stormborn," season seven's second episode, we catch a glimpse of Cersei's tactic for dragon murder. This, of course, begs the question: is it possible to kill a dragon? And if so, how?
In terms of the source material, it's pretty unclear how a dragon dies. There's no clear "How to Kill a Dragon 101" course buried in the novels. We do know that there used to be hundreds of dragons in Westeros, and at one point, they went extinct. Beyond that, the matter of how they died mostly falls on rumor and speculation. But hey, sometimes rumors are true. And rumors aside, there are plenty deadly weapons, materials, and objects in Westeros. Let's go over all the things that could potentially do the job (as well as the two things we know can definitely do the job).
In season five, Drogon sustains a few injuries during that fight sequence in the battle pits of Mereen. Between the spear in his side and the rain of arrows he endures, it's clear his skin is not entirely impenetrable. If a dinky spear and a bunch of small arrows are enough to break some skin, the logic follows that something bigger and more brutal would do the trick.
This is the most obvious answer, and it seems like it's the Lannisters' best bet. In the second episode of season seven, Qyburn unveils his plan to kill Daenerys's dragons through impalement. He presents to Cersei a gigantic crossbow, capable of launching a huge, deadly spear straight into the eye of a dragon, which he demonstrates on a huge, sturdy dragon skull. Two episodes later, in "The Spoils of War," Bronn puts the weapon to the test while Dany and Drogon attack the Lannister army. He's able to aim the crossbow perfectly and land the hit, although all it does is leave Drogon with a minor wing injury.
Long before the events of Game of Thrones, the Seven Kingdoms were ruled by the Targaryens. There were plenty of dragons around during this time, but many of them died out. One way these dragons are said to have died is in captivity. They simply stayed chained up and withered away. Given the fact that dragons are living, breathing creatures, their need for sustenance to live would be self-evident. It's not clear how long it would take to starve a dragon to death, but it seems like it's possible.
In the books, there are other rumors concerning the deaths of the previous dragons (as opposed to their weakening on their own). Some whispers suggested that the maesters, intent on suppressing magic in Westeros, poisoned the last of the dragons to put them into extinction. While it would have to be a pretty potent cocktail (and you'd have to get pretty close to administer it), poison seems like a pretty good bet. We imagine their insides aren't as indestructible as their scaly outsides.
4. White Walkers
The White Walkers are a pretty formidable force, and they clearly have some sort of magic on their side. That, along with their ultradeadly weapons, makes it possible for them to take down a dragon, as we see in season seven's sixth episode, "Beyond the Wall," when one of Daenerys's dragons gets taken down for good. As Viserion is attacking the army of wights closing in on Jon Snow, the Night King throws a deadly sharp ice spear into the creature's chest, and he quickly falls to his death. While we initially found the idea of an ice blade piercing a (presumably boiling-to-the-touch) dragon's skin impossible, we have to take into account that it's a White Walker-made weapon — the spear is much sharper (and more magical) than the usual icicle.
5. Other Dragons
During the Targaryen reign, there was a huge civil war called "Dance of the Dragons." The various battles pitted dragons against other dragons, and often, only one would come out of the clash alive. The dragons would kill each other in various ways: ripping each other's wings off, going for the neck with their razor sharp teeth, and even fighting fire with fire.
I know what you're thinking: there are only three dragons on Game of Thrones, and they all belong to Daenerys! While that's true, there are a couple of things that could happen. In the books, Euron possesses what's known as a Dragonbinder. It's a horn that, when blown, supposedly gives its owner control over a dragon. If Euron also possesses this horn on the TV show, he could potentially gain control of one dragon and pit it against another.
There's another even crazier theory, too. In the season seven premiere, we see how the White Walkers have resurrected giants as Wights. If the White Walkers can kill dragons (see above), there's also a chance they could resurrect them as ice dragons. And, well, it's hard to say who would win between Daenerys's dragons and a resurrected dragon of the undead.
We all know Daenerys's famous quote: fire cannot kill a dragon. But we can't help but wonder about the effectiveness of fire's evil, magical twin sister, wildfire. The weapon has proven to be deadly on the show, and it can cut through almost any material, including steel. There's a strong chance it would do significant damage to a dragon as well.
7. Valyrian Steel?
Here's another weapon that may be able to kill a dragon. Valyrian steel has proven to be a pretty deadly material in Westeros. It's strong enough to kill a White Walker, which means it's capable of undoing some pretty serious dark magic. Logic would follow that, if Valyrian steel could kill one kind of magical creature, perhaps it could kill another.
Another material that can kill White Walkers, dragonglass is an obsidian-like material found in volcanoes. Again, if dragonglass is powerful enough to end the life of an undead ice monster, I'd be willing to bet it could hurt a dragon pretty bad as well.