WARNING: Spoilers ahead for House of the Dragon season 1, episode 1!The introduction of Aegon's dream in the House of the Dragon season 1 premiere has massive impacts on Daenerys Targaryen and Jon Snow's Game of Thrones endings. House of the Dragon's story begins about 172 years before Daenerys Targaryen is born, with the first episode exploring how Princess Rhaenyra Targaryen is officially named heir to the Iron Throne by her father King Viserys I Targaryen. Once the great houses swear fealty to Rhaenyra as the Princess of Dragonstone, the king confides in her the secret of Aegon the Conqueror's prophetic dream, which directly connects to Jon Snow and Daenerys Targaryen's stories in Game of Thrones.
Game of Thrones season 8 and the series finale have reputations for being incredibly divisive, particularly in regard to the swift defeat of the White Walkers and the reveal of which character ends up on the Iron Throne. Jon Snow spent all eight seasons of Game of Thrones uniting the realm against the threat of the Night King and the White Walkers, and once this battle was won, the twist that he was actually the trueborn son of Rhaegar Targaryen and Lyanna Stark seemed to indicate that he would end up on the Iron Throne. Meanwhile, Daenerys Targaryen's major storyline followed her pursuit of the Iron Throne in Westeros, which she finally achieved at the end of Game of Thrones season 8. However, taking the Iron Throne involved slaughtering innocents in King's Landing, leading the honorable Jon Snow to kill Daenerys and be exiled to the Night's Watch.
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In the end, neither of the last Targaryens ended up on the Iron Throne, as the new ruler of Westeros became Bran Stark, a.k.a the Three-Eyed Raven. Jon and Daenerys' Game of Thrones endings remain highly controversial, but House of the Dragon adds a new layer to their fates that also happens to recontextualize House Targaryen's role in Westeros. Not only does Aegon's Song of Ice and Fire dream indicate that Jon and Daenerys truly worked together to fulfill the Prince That Was Promised prophecy, but it further supports the notions that Jon should have killed Night King and Daenerys was never going to end up on the Iron Throne.
House of the Dragon's King Viserys I Targaryen reveals that before conquering Westeros, Aegon I Targaryen had a prophetic dream that foresaw the end of mankind. As a terrible cold winter came out of the North, a darkness would threaten the existence of the living. In order for the living to win the battle, a Targaryen king or queen would need to sit on the Iron Throne, with this descendant being strong enough to unite the realm against the cold and the dark. Viserys tells his heir, Princess Rhaenyra Targaryen, that Aegon called his dream The Song of Ice and Fire, with ice corresponding to the White Walkers and Night King while fire represented the Targaryens and their dragons. The Targaryens' purpose in Westeros wasn't based on pure ambition and a desire for power, but a necessity in order to save humanity.
The dream also aligns with Game of Thrones' oft-mentioned Prince That Was Promised prophecy, which Prince Rhaegar Targaryen had been obsessed with in the books. The Prince That Was Promised, a.k.a the Targaryen that would save mankind from the cold and dead, would come from the bloodline of Aegon the Conqueror, and more specifically, that of Princess Rhaenyra Targaryen. Of course, the connection to Game of Thrones reveals that Aegon's dream had actually foreseen Daenerys and Jon Snow (a.k.a Aegon Targaryen) - a Targaryen queen and king - successfully uniting the living against the dead.
This prophecy was never revealed in Game of Thrones' series, but George R.R. Martin has teased the existence of Aegon's White Walker dream since 2018. While it's unclear what impact this will have on Martin's upcoming books in the A Song of Ice and Fire series, the dream is already changing what Jon and Daenerys' endings truly meant to the overall story. Game of Thrones' twist of Jon being a Targaryen always mattered in regard to his destiny in stopping the threat of the White Walkers, while Daenerys' ending would always require her dragons, multinational army, and brief time on the Iron Throne. However, Jon and Dany's heritage never meant they were supposed to stay on the Iron Throne, as Aegon's dream indicates that House Targaryen ruling Westeros was no longer necessary after the White Walkers were defeated.
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While it seems that The Mad King would have had to have known about the White Walkers if the prophecy was passed on through the House Targaryen family tree, the pre-Game of Thrones character's actions seemed to indicate he wasn't aware. On the other hand, Aerys' obsession with dragonfire, hatching dragon eggs, and wildfire may have been influenced by the Targaryens representing fire in Aegon's prophecy. Since Rhaegar had died, Daenerys and Viserys had already fled King's Landing, and Rhaegar's children had died, the Mad King wouldn't have had anyone to pass on the knowledge of Aegon's Song of Ice and Fire dream. It's thus no surprise that Daenerys and Game of Thrones' Viserys weren't aware of the Targaryens' true reason for being in Westeros, as the last children of King Aerys were motivated to take the Iron Throne simply due to it being their "birthright." However, the Game of Thrones books have several references to Rhaegar Targaryen's fixation on the Prince That Was Promised prophecy, hinting he may have known the truth.
Rhaenyra Targaryen says in a promo for House of the Dragon season 1, "From my blood come the prince that was promised, and his will be the song of ice and fire." This line was almost precisely what Rhaegar said during Daenerys' visions in the House of the Undying; as she saw her brother with a woman and baby, Rhaegar remarked, "Aegon. What better name for a king. He is the prince that was promised, and his is the song of ice and fire." While the other two figures were thought to be Elia Martell and their first son Aegon, House of the Dragon's Aegon dream suggests they were actually Lyanna Stark and Jon Snow, whose real name was also Aegon Targaryen. This would much better explain why Rhaegar became fixated on Lyanna Stark, as their child would perfectly embody "ice" and "fire."
Jon Snow being the Prince That Was Promised alongside Daenerys in Aegon's dream means he always should have been the Game of Thrones character to kill the Night King. Uniting Westeros against the White Walkers was the key motivation in Jon's story, and was thus the aspect of Aegon's dream that he would fulfill. Game of Thrones had been setting up Jon to kill the Night King for eight seasons, but when it came down to it, Arya Stark plunged the dagger instead.
Writing Jon to not kill the Night King remains one of the most criticized aspects of his Game of Thrones ending, and thus makes the show's choice to have Arya destroy the White Walkers even worse. As Aegon the First dreamed about a Targaryen bringing an end to cold and dark threat in the North, Aegon the Last was meant to see it through. Jon may have done the majority of the work in uniting the realm to save the living, but Arya will always be known as the one to bring an end to the White Walkers and Night King. Since Jon's House of the Dragon ancestors Rhaenyra and Viserys Targaryen are also seemingly shown to be in possession of the Catspaw dagger used to kill the Night King, it would have been far more poetic for him to be the one wielding the weapon as he fulfilled Aegon's dream.
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Jon's Game of Thrones ending realized Aegon's dream by protecting the living from the dead, while Daenerys' Game of Thrones story fulfilled it by landing on the Iron Throne. Aegon's dream may have said king or queen, but it really should have referred to a Targaryen king and queen. Daenerys was the Targaryen queen who brought fire from her dragons, united Westeros and Essos against the dead, and took the Iron Throne as the prophecy predicted. She had just as much of a part to play in fulfilling the prophecy as Jon did, and her Game of Thrones ending still supports this notion.
House Targaryen's ambition for the dangerous Iron Throne was necessary up until the point that the prophecy came true and the White Walkers were defeated. At this time, House of the Dragon's family had no purpose in claiming the Iron Throne as their birthright. Aegon's dream foresaw a Targaryen on the Iron Throne in order to defeat the Night King, but it never meant a Targaryen would rule Westeros thereafter. Ambition for ambition's sake wasn't the reason the Targaryens truly needed the Iron Throne, so when Dany slaughtered King's Landing at the end of Game of Thrones to reclaim her "birthright," she was acting outside the prophecy that predicated the family's regality. The dragonfire of Balerion the Black Dread in Aegon's conquest was a brutal means to an end to get the Targaryens on the throne and unite the Seven Kingdoms against a common enemy, not a way to separate the regions by unjustly murdering thousands with the simple motivation of power on the Iron Throne.
Daenerys dying and Jon abandoning all titles and claims was an apt conclusion to the Targaryen reign, and fell in line with Dany's aspiration to break the wheel. House of the Dragon now reveals that all along the Targaryens ruled with the underlying intention of saving the common people, with Jon and Daenerys both fulfilling their prophetic duties before bringing the House Targaryen family line to an end. Aegon never saw what the Targaryen future would hold after his dream, so it makes sense that there actually would be no future for them when the White Walkers died in Game of Thrones.
New episodes of House of the Dragon release Sundays on HBO/HBO Max.