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. Named after a Valyrian god, 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, and he also took part in the Field of Fire, the final battle of the War of Conquest in which he, Vhagar and Meraxes fought together. He was later ridden by Aegon the Conquerer's nephew, Maegor the Cruel, who used him in his war against the Faith Militants and had the dragon destroy the Sept of Remembrance. 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.
In the TV Series
Balerion is mentioned by Viserys Targaryen, elder brother to Daenerys Targaryen, as the dragon who forged the Iron Throne with his breath. His skull, the only part of him to appear, is stored in the cellars of the Red Keep on Robert Baratheon's orders. In season 7, Balerion's skull is used as a target for a scorpion ballista created by Qyburn, the hand of the late Robert's wife, the queen Cersei Lannister, to show that dragons are not invincible. The resulting test ends with the bolt fired from the ballista piercing the dragon's skull with one shot.
- Balerion on the Game of Thrones Wiki
- Balerion on A Wiki of Ice and Fire