Balerion, nicknamed the Black Terror or Balerion the Dread, was one of the three great dragons of Aegon I Targaryen and his sisters, who was used to conquer much of Westeros during the War of Conquest.
Along with other Targaryen dragon skulls, the enormous skull of Balerion was hung on a wall in the Throne Room of the Red Keep. After the War of the Usurper, Robert removed the skulls and put them in the basement. He liked to go down occasionally to look at it and the other skulls. He would even take his mistresses down there sometimes, according to Cersei.
Balerion is mentioned by Viserys while taking a bath with Doreah. He also adds that his flames were used to forge the Iron Throne.
Enthused by her readings, Shireen Baratheon tells Davos Mervault about her book on Balerion's history, and even claims that his skull would still be visible in the Red Keep today.
Later, Davos explains to his father that trying to conquer the Seven Crowns through blood magic is both futile and evil. Stannis replies that this is how Aegon conquered Westeros even though he had a smaller army than his opponents, thanks to his dragons, which are magical creatures.
Qyburn takes Queen Cersei Lannister into the basement. He shows her the famous skull of Balerion, bigger than all the others. He says it must have been a powerful specimen but not invincible. He then tells Cersei that Daenerys' dragons would have been injured in the battle pits of Meereen. He goes on to say that if they can be hurt, they can also be killed.
Qyburn then unveils a ballista, explaining that it was designed by the best engineers in the capital. Aimed at the skull of the deceased Balerion to test its effectiveness against a dragon's bone structure, the weapon's powerful stroke manages to penetrate a large part of the skull, which would instantly kill a living dragon.
Later, while heading to Fossedragon for the King's Landing Talks with his allies, Tyrion states that Fossedragon certainly became the most dangerous place in the world when it became Balerion's home.
Balerion was the largest of all the Targaryen dragons, his teeth were as long as swords and his jaws were large enough to swallow a herd of mammoths. His flames were as black as his scales, and his wings were so large that he could fly over an entire city and put it in shadow.
Balerion was named after the ancient deity of the Possessions. He was born in Valyria. Balerion was one of the five dragons that Aenar Targaryen took with him when he fled to Peyredragon to survive the Scourge of Valyria.
He earned the nickname "Black Terror" during the Conquest, where Aegon rode him repeatedly to conquer Westeros. He became famous when Aegon used him against King Harren Chenu during the Fall of Harrenhal. Balerion's flames burned the towers of Harrenhal, which melted like candles.
King Harren and his sons all perished. Balerion also participated in the Field of Fire, the only time in history that all three legendary Targaryen dragons took to the skies at the same time. Along with Vhagar, Meraxes and Balerion, 4,000 men were burned, including King Mern. His death led to the extinction of the Garden House. The army was destroyed and Aegon I was victorious.
Balerion is said to have forged the Iron Throne by melting the swords of Aegon's defeated enemies. Aegon the Conqueror only rode Balerion to fight or to travel. After Aegon's death, Balerion was claimed by his son Maegor, who had long coveted his father's throne and was not given another dragon, because he considered all others unworthy. When he was exiled, Maegor rode Balerion to Pentos.
After the death of his brother Aenys, Maegor flew to Westeros on the back of Balerion to claim the Iron Throne. During his reign as king, Maegor used Balerion to destroy the Shrine of Remembrance and in many other battles against the Militant Faith. During the Battle Under the Gods, Maegor used Balerion to kill his nephew Aegon and his dragon Silverthread.
Balerion was then ridden by Viserys I Targaryen, while he was still a prince, during the reign of King Jaehaerys I Targaryen. Balerion died of old age in the year 94. He was about 200 years old when he died. Viserys never wanted another dragon. He was on Balerion's back at the time of his death.
