The first episode of House of the Dragon went hard with the lore of George R.R. Martin's novels. In The Heirs of the Dragon, we got to learn the truth about Aegon I Targaryen's vision that prophesized the end of the world of man. In addition to that, it turns out that the Targaryens were well aware of the arrival of the Night King and the White Walkers.
This was a truly eye-opening revelation for fans who have had theories about the Song of Ice and Fire since the first few seasons of Game of Thrones. However, it also led to many questions. For instance, was Daenerys Targaryen aware of the prophecy?
House of the Dragon: What is the Song of Ice and Fire?
In House of the Dragon Episode 1, Viserys took Rhaenyra Targaryen to the Red Keep where he tells the princess about Aegon the Conqueror's reason for conquering and then uniting the seven kingdoms.
As it turns out, Aegon had a vision of the fall of man and needed to ensure that Westeros was united when a long winter finally came. Aegon called his dream "The Song of Ice and Fire" and prophesized that a Targaryen should be on the Iron Throne to lead Westoros in the fight against the White Walkers.
House of the Dragon: Did Daenerys Know About Aegon's Prophecy?
In Game of Thrones, Daenerys Targaryen was the only surviving Targaryen royal who was actively gunning for the Iron Throne after the death of her brother Viserys. However, it was established that Dany was completely unaware of the arrival of the White Walkers until Jon Snow told her about the icy undead.
So why didn't Daenerys know about the Song of Ice and Fire? The answer is in House of the Dragon Episode 1. King Viserys only told Rhaenyra about the prophecy when she was chosen as his successor. Since the information is only shared between ruler and heir, Dany's father may have told his own successor about the vision.
Dany was never considered the heir prior to King Aerys' death because he had a son Viserys who could take the Iron Throne after him. Viserys may have known considering that he was aiming to reclaim the Iron Throne but unfortunately, he was killed by Dany's husband Drogo before we knew the truth.