The Game of Thrones canon is packed with sneaky assassinations. Everything starts when Lysa Arryn feeds her husband Tears of Lys, a deadly fictional poison. And poison resurfaces again and again throughout the series, with characters like the Baratheons and Daenerys Targaryen being targeted by poisoning attempts.
And the season premiere for season seven was no different.
Spoilers for the season premiere of Game of Thrones are ahead, obviously.
In perhaps the most badass cold open of television history, Arya Stark avenged her family by eradicating House Frey without spilling a drop of blood. Using the training she received from the Faceless Men of Braavos to impersonate Walder Frey, Arya leads the remaining Freys in a toast — of poisoned wine.
Our best guess at what poison Arya used is the fictional Long Farewell, though this doesn’t explain why the dying Freys were coughing and vomiting blood so rapidly. There are, however, a number of real-world poisons whose effects come pretty close.
In Westeros and on Earth, vipers are among the most deadly animals out there. Vipers, which fall under the Adder family of snakes, transmit lethal venom with their bites.
While not much is known about Westerosi viper biology, the venom of a real viper can cause pain, swelling, and vomiting and diarrhea, both of which could contain blood. In severe cases, viper venom can cause paralysis, shock, and kidney failure before people die from puking out all their blood.
To be effective, however, viper venom needs to be actively introduced to the bloodstream, because it’s pretty harmless when it’s ingested. If Arya did indeed spike the wine with viper venom, she would have had to know that everyone in the room had a small cut on the inside of their mouths for the venom to enter the bloodstream.
The effects of arsenic poisoning most nearly match what happened to the Freys. The tasteless, odorless white powder was, historically, mixed into beverages by assassins, and was still commonly used in the 20th century. It is one of the few poisons that causes people to vomit blood.
People with arsenic poisoning develop headaches and nausea before the more serious symptoms — vomiting, diarrhea, convulsions, and severe pain — set in. Because it took only a few seconds for the Freys to notice their symptoms, and they all died within the span of Arya’s short speech, Arya would have had to use a seriously high dosage. Depending on the concentration, arsenic poisoning can take anywhere from two hours to four days to kill someone.
While very few poisons reliably make people vomit blood, there are some that can still corrode or tear holes into people’s esophagi or guts, and induce nausea. One particularly potent poison that does this is hydrochloric acid, an intensely corrosive acid.
At the right concentration — around three moles of acid per liter of water — hydrochloric acid could cause some serious hurt and burn away any flesh with which it comes into contact. For reference, the powerful acid in your stomach that breaks down your food contains just one-tenth of a mole per liter of water.
Also, hydrochloric acid poisoning could take effect as quickly as the Frey massacre took place. The hardest part about poisoning someone with hydrochloric acid is that, unlike powdered arsenic, it’d be much harder to mask the presence of the acid with wine.
Powerful acids cause damage the second they touch someone’s unprotected skin: Unless the Freys were already obliterated off some blackwater rum, they would have noticed something was wrong the second they put their glasses to their lips. Once they swallowed, they would quickly develop a swollen throat, a fever, and severe pain the whole way down from the mouth to the belly. Arya may have wanted to cause a painful death for her enemies, but if she had used hydrochloric acid she wouldn’t have been able to make it through her speech before the Freys started screaming in agony — and that would have been way less satisfying.
Many poisons — like cyanide and ricin, as well as heavy metals like thallium — can also cause nausea and vomiting. But with these poisons, it’s less likely that victims will also vomit blood.
There are reports of people coughing up blood because they’re so sick and strained that small tears will occur somewhere in their esophagus or stomach, and the blood from there gets expelled. For example, the prescription blood thinner warfarin can cause serious side effects like nosebleeds, coughing up blood, prolonged bleeding from existing wounds, and bloody gums, stool, and urine. While it’s unlikely that Arya had access to warfarin, she could have heard about dicoumarol, a chemical found in a type of mold that grew on clover from which warfarin was later synthesized. The mold was discovered when farmers found herds of dead cattle near the plant.
We may never know how Arya Stark orchestrated the demise of House Frey so masterfully. But her cold, unaffected gaze as she told Walder Frey’s widow that “Winter came for House Frey” made one thing clear: We can expect much more clever, insidious bloodshed from the youngest Stark daughter.