In the comic book world, writers and artists always warn fans that they should worry when good things happen to their favorite characters. Nothing good — new friends, new lovers, new leases on life, new bits of happiness — can last in a universe built on high-stakes peril and drama.
Cersei has absolutely throttled this young seventh season by handily outmaneuvering her biggest foes. She got rid of sneaky, shady Olenna Tyrell by sending a surprise attack to Highgarden. She forged an alliance with the newly made-over Euron Greyjoy to sink Dany’s battleships. In the process, two of the three Sand Snakes were killed and one was captured — only to be finished off by Cersei in a two-for-one special as the queen poisoned her prisoner while keeping the Snakes’ mother alive to watch her daughter die (the show implies that the death happens offscreen).
That’s in addition to indulging in unapologetic incest with her brother Jaime, and traipsing around the castle the morning after like Julie Andrews in The Sound of Music — she doesn’t have a care in the world about what people might say about her, now that she’s the queen.
High on the thrill of violence inflicted upon her enemies and gentle postcoital spooning with her brother/lover, there is no character on Game of Thrones who’s currently winning more than Cersei Lannister. Which means everything has to come crashing down around her sooner or later.
Cersei’s strategy has been sound, but her army is in a vulnerable position
The first three episodes of season seven have hammered home that Dany doesn’t want to attack King’s Landing because she doesn’t want her dragons to turn the place into the Targaryen Bar and Grill. Not being able to separate civilians from Cersei’s army is all that seems to be holding Dany back, and is the main reason Tyrion keeps reminding her that there’s no power in ruling a city of ash.
Meanwhile, the detail that’s stopping Dany from retaliating against Euron by torching his fleet, as stated in “The Queen’s Justice,” is that she doesn’t know where he is or what kind of support he has.
But we viewers know Euron’s exact whereabouts: As we witnessed at the end of the episode, he’s closing in on Casterly Rock, which the Unsullied have just taken. And Jaime has marched his army to Highgarden.
Which suggests that for both Dany and Cersei, lots of things are about to change.
Grey Worm will probably get word to Dany that Euron has arrived in Casterly Rock, which may prompt her to send her dragons, flank Euron’s navy, and burn his ships in the open water. The question is whether they’ll arrive in time to save Grey Worm and the Unsullied.
If this conflict were about to play out in any other location, the odds would favor Euron’s powerful navy. But in “The Queen’s Justice,” we learned an important secret about Casterly Rock: Though it’s really difficult to break into because of its walls and design, its sewer system is vulnerable — and the only people who know about that vulnerability are the Unsullied and the man who created it, Tyrion Lannister.
With Casterly Rock’s defenses, the Unsullied should be able to last long enough for Dany and her dragons to come swooping in and save the day. Since Euron doesn’t know about the sewer system, the Unsullied should be able to hold him off in time for some dragon-fueled reinforcements or to prepare a retreat.
Meanwhile, it’s unclear what Jaime’s army is planning to do or where it’s going to go after plundering Highgarden. Perhaps they’ll team up with Euron to take back Casterly Rock. But every second they’re on the march, they’re at risk — they’re conveniently separated from the civilians from King’s Landing, which until now has been the only thing protecting them from Dany’s dragons. And they’re also easy target for Dany’s dragons if they’re marching in open fields.
Another reason the future might not be so great for Jaime and his army: This little snippet from the season seven trailer shows him riding through a scorched, fire-ridden field (which could be a sign that he’s about to encounter a very angry Dany):
It’s extremely plausible that in two swoops by three dragons, Cersei could see large parts of her army and/or navy completely demolished.
Given how malevolent and successful Cersei has been so far this season, it doesn’t feel like a question of whether her downfall will happen so much as when it will happen.
But even with the assumption that she’ll lose her lead, I wouldn’t put it past Cersei to have one last colossal betrayal up her sleeve, either later this season or in Game of Thrones’ eighth and final one. She’s shown us before that in her world, despair, like success, is only temporary.