Perhaps the most fantastical element from the fantasy universe of Avatar: The Last Airbender was the dragons the series so rarely showed. The series explained their rarity as the result of being hunted to near-extinction during the time of Fire Lord Sozin, and made a plot point out of the species barely hanging on to its survival. However, hints elsewhere in the series seem to indicate that the relationship between humanity and dragon-kind was rife with problems well before Sozin began overhunting.
Piecing together the Avatar lore related to dragons, it's clear that there may be far deeper issues than the series directly addressed. Sozin may have brought the species to near extinction, but he likely wasn't the first human to show the fire-breathing lizard just how awful some people can be.
Little is known about dragons in Avatar, and they are only seldom seen. In the chronology of the world, one of the earliest appearances is during the days of the first Avatar, Wan, when he learned to properly firebend by studying the Dancing Dragon motions from a white dragon present during ancient times. Thousands of years later, during Aang's childhood, the young airbender said that there were tons of dragons, as he desperately sought to ride one alongside his Fire Nation friend Kuzon. However, after Aang was frozen for 100 years, he awoke to a world where dragons were believed to be extinct following Fire Lord Sozin imposing a tradition of hunting down the beasts to earn the title of "Dragon" for themselves.
Iroh, known as the "Dragon of the West," was believed to be the last human to see a dragon alive after he killed the final one to earn his title. This is later revealed to be a lie that Iroh constructed to protect the last two dragons, Ran and Shaw, who are worshipped by the secret civilization of Sun Warriors and who later make Aang and Zuko swear to maintain their secrecy. Still, there are a few puzzling questions that raise concerns about humanity's relationship with dragons even before Sozin's time. Namely, if the Sun Warriors formed in the days before there was even a Fire Nation, what exactly were they hiding Ran and Shaw from if dragon-hunting only became a severe problem in Sozin's day?
Indeed, despite Aang saying that there were tons of dragons during the days before the Hundred Year War, the rarity and shyness of the creatures proves justified during his adventure with Kuzon. After scouring mountaintops to find a dragon, the pair come across poachers looking to steal a dragon's egg. Aang and Kuzon manage to scare the poachers off, but the fact that there was a poaching practice at all, and that it was even known as "poaching" at the time, would suggest that overhunting or otherwise threatening dragons' existence was already a longstanding problem.
The only reason the Sun Warriors would have for receding from society and keeping Ran and Shaw a secret so long before Sozin's time is if humankind already had a relationship with dragons rife with its own issues. Far from proving bent on the destruction of the species, Sozin himself was shown to have a dragon as a mount at the same time as Roku had his own dragon, Fang -- so even if the Fire Lord were to start the tradition of hunting them down, it would have been in the waning days of his life.
Moreover, it's hard to believe that such powerful creatures could be hunted to near-extinction within the span of little more than a century, especially a century in which Fire Nation efforts were primarily focused on the growing Hundred Year War rather than leisure activities like hunting.
Luckily, dragon-kind seemed to recover over the course of Fire Lord Zuko's reign, as he was shown with his own mount, Druk, in the days of The Legend of Korra. Nonetheless, there is clearly a far darker history that Avatar has yet to fully explore.
Prequel novels like the Kyoshi books are the exact kind of material where the franchise could give further insight into what the relationship between humans and dragons was like. Despite venturing to the Fire Nation in the second novel, however, the prequel stories have yet to delve much further into what that mythology is like.
