You could read about Balerion the Dread.
Game of Thrones Season 3, Episode 10
But in the beginning, when it was home
to Balerion the Dread,
Game of Thrones Season 7, Episode 7
Balerion the Dread.
Game of Thrones Season 7, Episode 2
forged in the fiery breath
of Balerion the Dread.
Game of Thrones Season 3, Episode 6
I know. But still it filled me with DREAD.
Game of Thrones Season 4, Episode 8