A 'Game of Thrones' prequel series, 'A Knight of the Seven Kingdoms: The Hedge Knight,' is officially greenlit Madison Durham, Reviewed Updated April 12, 2023 at 2:22 PM · 3 min read The largest dragon in the history of Westeros was Balerion the Black Dread, whom Aegon Targaryen rode when he conquered the Seven Kingdoms. Balerion was roughly 125 years old when the two first Fantasy. Game of Thrones. The Conquest of Dorne was a war waged by King Daeron I Targaryen, the Young Dragon, to bring Dorne under the authority of the Iron Throne and finally unite all of the Seven Kingdoms. Daeron I sought to succeed where even King Aegon I Targaryen had not, and conquer Dorne in the name of House gRE4oaH.