The Season 3 finale of House of the Dragon depicts Aegon II confronting his brother Aemond at Harrenhal after they had been estranged since the Battle of Rook's Rest, marking a significant departure from the storyline in George R.R. Martin's source book, Fire & Blood. In the show, Aegon spends much of the season adrift in the Riverlands with Larys Strong before reuniting with his dragon, Sunfyre, and resolving to reclaim the Iron Throne, setting up a direct confrontation with Aemond that has no equivalent in the book.

This change matters because it signals potential further deviations for other characters heading into Season 4, as the series continues to diverge more substantially from its source material than in earlier seasons. Aemond, meanwhile, is portrayed as broken by Alicent's attempt to poison him and by his belief that he had killed Aegon at Rook's Rest, making the brothers' reunion at Harrenhal an emotionally charged moment unique to the television adaptation.