Dragons

Dragons are creatures that once existed on the continents of Westeros and Essos, but are believed to have been extinct for over a century and a half.

In the books
In the Song of Ice and Fire novels, dragons are described as four-limbed creatures (two legs and two wings with foreclaws). They are native to the continent of Essos, and were found in significant numbers some five thousand years ago on the Valyrian Peninsula. The people of Valyria tamed the dragons and used them as steeds and weapons of war. Using dragons they forged a vast empire spanning most of the continent until the event known as the Doom destroyed the empire and eliminated most of the dragons. The only dragons known to have survived were the three dragons belonging to House Targaryen, which used them to conquer the Seven Kingdoms.

The Targaryens kept their dragons for approximately one hundred and fifty years and at one time had a significant number of the creatures, at least nineteen (this is the number of dragon skulls at one time stored by the Targaryens in the Red Keep). Most of them were killed in the Targaryen civil war known as the Dance of Dragons. The surviving dragons were weak and sickly, with the last dragon dying during the reign of King Aegon III Targaryen, the Dragonbane. The last dragons left behind several eggs, which never hatched. These eggs were later destroyed or lost to the vagaries of history. As a result, dragons are now considered to be extinct.

According to Valyrian records, dragons hatch small, about the size of an average dog, but grow larger and larger as their appetites expand. A dragon never stops growing as long as it remains fed. Dragons could live to be over 200 years old, and it is said that Balerion the Black Dread, one of Aegon I's dragons, was so huge when he died he could swallow an aurochs whole. Dragons could breathe fire and were ferociously strong. However, they were also vulnerable to sustained arrow fire from the ground, to poison and to attacks from other dragons. The art of taming and commanding dragons enough to ride is almost unknown aside from a few exceedingly rare books.