"Rhaenys was a child too. Prince Rhaegar's daughter. A precious little thing, younger than your girls. She had a small black kitten she called Balerion, did you know? Rhaenys liked to pretend he was the true Balerion, the Black Dread of old."
“Balerion's scales and wings were black. His fire was black, sometimes with swirls of red. When he was in the fullness of his power, his flames could melt steel and stone, and fuse sand into glass.”
-A Wiki of Ice and Fire
“The first time Baelon visited the Dragonpit, he hit Balerion on the snout, causing Ser Samgood of the Kingsguard to remark that he was either brave or mad. Ever since, Baelon was also known as Baelon the Brave.”
-A Wiki of Ice and Fire
"Balerion the Black Dread was two hundred years old when he died during the reign of Jaehaerys the Conciliator. He was so large he could swallow an aurochs whole. A dragon never stops growing, Your Grace, so long as he has food and freedom." -Ser Barristan.