The New Game of Thrones Trailer Has Sparked So Many Wild Theories

Meanwhile, all the way down in Casterly Rock, it seems that Grey Worm is leading an ambush on Lannister territory. As a reminder, Tyrion was in charge of overseeing the sewer system when he was on duty. Could he be the one behind this attack? In a later shot, we see a handful of the Unsullied letting more of their own men in through some gates. This could be some Trojan War kind of sneakiness.