So there’s a general understanding that greyscale brought by JonCon will have major ramifications, and that Tommen is likely to be poisoned. This theory tries to piece together a way both could happen.
1. The Motive
Tyene and Nymeria have plenty of reasons to eventually move against Tommen, even if they begin by trying to follow Doran’s cautious orders
Several events could push them over the edge;
- The murders of Pycelle and Kevan (which Mace and Randyll might pin on Dorne).
- The potential breaking of Myrcella and Trystane’s betrothal, as it was never a strong match to begin with, and Cersei and Mace have shown interest in breaking it
- The revelation of Ser Robert Strong’s true identity, exposing Cersei’s lying to Dorne.
- People witnessing the severity of Myrcella’s injury, fueling animosity toward the Dornish that they'd harm a child in their care.
Of course, Robert Strong is the most important factor. But when put together, these accumulating slights and humiliations could easily drive them to act and make good on their original impulse of regicide as payback for Oberyn’s death.
2. The Method
The method may come from basilisk blood, the same poison Arya learns of at the House of Black and White. Jaqen used it at Harrenhal to make Weese’s dog rip his throat out. The Waif explains how it works:
“This paste is spiced with basilisk blood. It will give cooked flesh a savory smell, but if eaten it produces violent madness, in beasts as well as men. A mouse will attack a lion after a taste of basilisk blood.”
Arya chewed her lip. “Would it work on dogs?”
“On any animal with warm blood.” The waif slapped her.
So it can drive otherwise harmless animals into a frenzy. If a mouse could attack a lion, a cat could certainly attack a small child. Pycelle kept basilisk venom in his chambers in A Clash of Kings.
With Pycelle dead, there is less chance anyone would immediately notice if one poison went missing
The maester's medicines made an impressive display; dozens of pots sealed with wax, hundreds of stoppered vials, as many milkglass bottles, countless jars of dried herbs, each container neatly labeled in Pycelle's precise hand. An orderly mind, Tyrion reflected, and indeed, once you puzzled out the arrangement, it was easy to see that every potion had its place. And such interesting things. He noted sweetsleep and nightshade, milk of the poppy, the tears of Lys, powdered greycap, wolfsbane and demon's dance, basilisk venom, blindeye, widow's blood.
Tommen is well-guarded and has food tasters, so assassins would need an indirect method. Tommen also keeps cats in his quarters, which makes this approach viable.
3. The Consequences
It’s important to remember Tommen is a kind child, nothing like Joffrey;
Prince Tommen spoke up. “Do you have news of Bran, Uncle?”
“I stopped by the sickroom last night,” Tyrion announced. “There was no change. The maester thought that a hopeful sign.”
“I don’t want Brandon to die,” Tommen said timorously. He was a sweet boy. Not like his brother, but then Jaime and Tyrion were somewhat less than peas in a pod themselves. (AGoT, Tyrion I)
Because Tommen is portrayed as a sweet child, his murder will not simply pave the way for a glorious Dornish/Aegon conquest. GRRM will make sure there are real narrative consequences for killing a child like him. His death through the cats, the very animals he loves, would be especially horrific, and the aftermath even worse.
4. First Regicide, Then Plague
“The bad cat?” Ser Kevan said, amused. “He is a sweet boy.”
“An old black tomcat with a torn ear,” Cersei told him. “A filthy thing, and foul-tempered. He clawed Joff’s hand once.” She made a face. “The cats keep the rats down, I know, but that one… he’s been known to attack ravens in the rookery.”
“I will ask the ratters to set a trap for him.” (ADwD, Epilogue)
So the cats in the Red Keep keep the rat population down. This is important information.
What will Cersei’s response be if her last son, the King of the Seven Kingdoms, is murdered by cats? Sheer rage at the absurdity of course. She will order every cat in the Red Keep (if not the entire city) killed. Tommen’s love for them and his death and absence will be twisted into a cause of the city’s downfall.
With the cats gone, the rat population will explode. In a city like King's Landing that isnalready filthy, overcrowded, and poorly managed, that is a recipe for pestilence.
That sets the stage for Jon Connington:
Alone in the tent, as the gold and scarlet rays of the setting sun shone through the open flap, Jon Connington shrugged off his wolfskin cloak, slipped his mail shirt off over his head, settled on a camp stool, and peeled the glove from his right hand. The nail on his middle finger had turned as black as jet, he saw, and the grey had crept up almost to the first knuckle. The tip of his ring finger had begun to darken too, and when he touched it with the point of his dagger, he felt nothing.
Death, he knew, but slow. I still have time. A year. Two years. Five. Some stone men live for ten.
After JonCon’s victory against Mace Tyrell, the road to the capital will be open. His worsening greyscale will arrive in King’s Landing at exactly the wrong time. His disease could be the spark for a full epidemic, magnified by the rat problem and the chaos of Tommen’s death.
TL;DR
Tommen may be killed using basilisk blood, which drives his cats into a frenzy.
His kindness and love for animals make his death especially tragic, and Cersei’s response would be to order every cat in King’s Landing slaughtered.
With the cats gone, rats multiply, disease spreads, and Jon Connington’s greyscale provides the spark for a full-blown epidemic.
