In Game of Thrones and A Song of Ice and Fire, Balerion the Black Dread was the dragon of King Aegon I Targaryen, known also as Aegon the Conqueror, who helped the king to win the War of Conquest. Balerion was massive and powerful; said to be big enough that his shadow while flying swallowed whole towns. He could swallow horse and rider whole and his flame, black and red as he was, was hot enough to melt stone. Balerion's fire was used to forge the swords of Aegon's enemies into the Iron Throne. Of the three Targaryen dragons to participate in the War of Conquest, only Vhagar approached him in size, and only then after many decades.
Balerion is known to have burnt down Harrenhall, he also took part in the Field of Fire, the final battle of the War of Conquest. He was later ridden by Aegon the Conquerer's nephew, Maegor the Cruel. He later killed the smaller dragon Quicksilver in the Battle Beneath the Gods Eye and his rider Aegon II, Maegor's nephew. He died of old age nearly a century later under the reign of Jaehaerys I Targaryen. His rider at that time was Viserys I, who was the last Targaryen to pair with the black dread. At the time of his death Balerion was at least 200 years old. Many believe that Drogon, the eldest sibling of Daenerys Targaryen's three dragons, to be Balerion reincarnated.
- Balerion on the Game of Thrones Wiki
- Balerion on A Wiki of Ice and Fire