Warning: Contains SPOILERS for House of the Dragon season 1, episode 1.The reveal of Aegon the Conqueror's dream in House of the Dragon supports a wild Game of Thrones theory about the Mad King, Aerys II Targaryen. Although it was expected that House of the Dragon would have some connections to Game of Thrones, it perhaps hadn't been anticipated to have such a tangible impact upon its parent show right from the very first episode. That's exactly what happened though, as House of the Dragon season 1, episode 1's ending revealed Aegon's dream of the White Walkers, which serves to change and reframe much of what's known about House Targaryen's history.
Much of that is inevitably on how it changes Jon Snow and Daenerys Targaryen's stories, since both were actually Targaryens alive when the White Walkers eventually came, with each playing their part in defeating them (though neither sat the Iron Throne). In particular, it makes Jon's Targaryen heritage feel important in a way Game of Thrones never fully managed, and seemingly conflates Aegon's dream with the Prince That Was Promised prophecy, with both surrounding the idea of a hero who'd lead the living to victory over the dead. But it goes further than just Jon and Dany; Rhaegar was obsessed with prophecy, for instance, and that makes more sense with this knowledge... but what about his father, Aerys II, aka the Mad King?
One of the wildest theories to come from Game of Thrones was that Bran Stark drove the Mad King to his madness. This came from one of Bran's visions when training to become the new Three-Eyed Raven, which included the Mad King saying "burn them all." The theory suggests that Bran, like he did with Hodor, messed with time and tried to warn the Mad King of the White Walkers, but it didn't exactly work. The Mad King was then seeing the White Walkers when he was yelling "burn them all." For various reasons - not least how much it changes the story, but also a greater lack of evidence for it - it was very much a tinfoil Game of Thrones theory, but House of the Dragon's reveal of Aegon's dream does curiously support it. If the prophecy was passed down from King to heir, then did the Mad King know about the White Walkers after all?
Did Game Of Thrones' Mad King Know About The White Walkers?
It would certainly be fascinating if Aerys knew about the White Walkers, and add another layer to the Mad King's plan for destroying King's Landing. It wouldn't necessarily confirm the theory that Bran was responsible for the Mad King, but does provide more connective tissue than existed previously. There's no denying the Mad King was a terrible ruler who committed several heinous acts during his reign, and that this was driven by the supposedly inherent Targaryen family madness (the Gods flip a coin, etc) and his own increasingly paranoia and cruelty, but whether that was made worse because of his knowledge of the White Walkers, and the burden that carries, is now unclear and at least a possibility to be considered.
Rhaegar, who was deeply invested in the prophecy of The Prince That Was Promised, had to get that from somewhere, so again there's a chance, even a slim one, that also came from Aerys. At the same time, it's also highly possible that House of the Dragon will reveal Aegon the Conqueror's dream was lost after the Dance of the Dragons, with neither of its claimants to the Iron Throne passing it on (if, indeed, Viserys' son Aegon learns the truth at all). That may well be the neater option, allowing for Rhaegar to discover a prophecy in a different way and bypassing too many retcons of House Targaryen history.
House of the Dragon releases new episodes Sundays on HBO and HBO Max.