Viserys has the distinction of being the last known rider of Balerion the Black, the largest dragon Westeros had ever seen, the former mount of Aegon the Conqueror, and the last living thing to ...

Aegon I mounted Balerion the Black Dread during the Targaryen Conquest of Westeros, and afterward, and Daenerys Targaryen rode Drogon when she came for the Iron Throne.