In episode 2 of Game of Thrones Season 7, Qyburn revealed to Cersei Lannister that his minions had been working on the middle ages style version of an anti air-dragon missile ahead of facing Daenerys Targaryen. (Otherwise known as a Very Large Crossbow.) But is that how you kill a dragon in the world of Westeros? Can humans kill dragons on Game Of Thrones?
The good news for Cersei: The answer is yes. Humans have killed dragons before. The good news for Dany: The answer is not very often. When we go back through Martin's histories of dragon-based battles in Westeros during the early Targaryen period, we find that far more dragons have died via dragon-on-dragon violence than via anything humans have been able to cook up.
In truth, the thing that killed the most dragons at any one time was the Doom of Valyria, where the ring of volcanoes that ran through the peninsula all erupted at once. Prior to the Doom, dragons numbered in the hundreds across that part of Essos. After the Doom was over, there were only five left living on Dragonstone with the Targaryen clan, and they were an essential part of their conquest of Westeros.
There were 27 dragons who were recorded to have lived during the 150 or so year period from the Targaryen conquest to 153 AC when the final dragon died out. Of these 27, only nine died of natural causes. The other 18 were all killed in battle. Of those 18, ten were killed by their own kin.
That leaves only eight dragons who have been killed by humans:
- Meraxes: Killed by a scorpion bolt through the eye.
- Stormcloud: Killed by several crossbolts and scorpion bolts during The Battle of the Gullet.
- Vermax: Drowned by crashing into a boat and being taken down in the wreckage during The Battle of the Gullet.
- Dreamfyre, Morghul, Shrykos, Syrax, and Tyraxes: All five were killed by a fire bearing mob during the King's Landing riots during the Dance of Dragons, three of them while still in chains in the Dragonpit (Morghul, Skrykos, Tyraxes). Dreamfyre was killed as she tried to escape the pit, and Syrax as she swooped down from the Red Keep to attempt to rescue her kin.
In terms of Qyburn's idea then, this is not the worst thing he's come up with. Two of the eight dragons listed here died via crossbolts, though neither of a size he's working on. Instead, it's either been due to the sheer volume or a lucky shot.
But what Dany should probably fear more is the deaths of those other five, more than half the list. Now, her dragons are not chained up helpless like three of these dragons were. (In fact, this is more argument that she should never do what she did in Meereen to Viserion and Rhaegal ever again.) But this is proof that sheer numbers of angry frightened violent humans are as dangerous to dragons as a crossbolt, and a wounded dragon crashing down in the center of a Lannister army would be at their mercy.
Let's hope she flies carefully.