20 dragons are alive at the beginning of the Dance of Dragons, with only 4 surviving. ... Game of Thrones, dragons are long extinct until the hatching of Daenerys Targaryen's three dragons.

Daenerys rides Drogon for the first time at the end of A Dance with Dragons, just like she does in Game of Thrones season 5, but Drogon's wings are described as being roughly twenty feet in the novel.

As the long wait continues for George R.R. Martin's next novel, the 13th anniversary of A Dance with Dragons is giving me new Game of Thrones regrets.