Game Of Thrones Season 7 Implications: What "The Queen's Justice" Really Means

2. Casterly Rock Falls, But It's No Victory

Having obviously watched Lord Of The Rings recently, Tyrion told Dany that he knew of a backdoor into Casterly Rock, after his father forced him to design the sewer system. Since he absolutely loved prostitutes, the Imp had built in a secret entrance that they could use to come and service him away from the prying eyes of his disapproving father.

That was then used as a means to circumvent the Lannister defences (though lots of Unsullied were still sent to their deaths at the foot of the walls, which seems a little unnecessary, but that's how the tactics of war work in Westeros.

Despite being promised a huge defensive force, the Unsullied met little resistance and took the castle simply, which inevitably confused Grey Worm (still with a giant Dead Meat label hanging over his head). Of course, this was thanks to Jaime's superior tactics: he gave up Casterly Rock as a pointless trophy, took his forces to Highgarden and sent Euron's fleet to sneak up on the Unsullied fleet and destroy them.

So while Dany's forces took the castle, they're now stranded and under siege by the Greyjoys (and presumably some of the Lannister army now it's done with Highgarden). That's a fairly catastrophic problem for Dany, who is either going to have to fly in to rescue what remains of them (by fulfilling her vow to burn Euron from the air) or lose another huge swathe of her army.