Dragons are reptilian-like creatures that once lived all over the Known World. The dragonlords of the Valyrian Freehold managed to train them, allowing them to use dragons in battle and thereby greatly expand their domains. Forty dragon-riding families could be found in Valyria until the Doom came, which destroyed the Valyrian Freehold. All dragons present died, and the few that survived elsewhere in Essos did not long outlive them. Only House Targaryen, which had relocated from Valyria to Dragonstone twelve years earlier with five dragons, remained of all the dragonlords. On Dragonstone, the Targaryen dragons thrived.
During his conquest of the Seven Kingdoms, King Aegon I Targaryen used three dragons in battle: Balerion, Vhagar, and Meraxes. His eldest son was given a dragon of his own, and at a certain point it became tradition to present new-born Targaryen princes and princesses with a dragon's egg in their cradle. However, as dragons continue to grow as long as they are given plenty of freedom, the construction of the Dragonpit in King's Landing on the orders of King Maegor I Targaryen slowed the growth of the dragons the Targaryens held. The war known as the Dance of the Dragons greatly reduced the number of dragons alive, as both sides of the war used their dragons in battle against one another. While by the end of the reign of King Viserys I Targaryen twenty dragons were alive, only three of those survived the war (Sheepstealer, the Cannibal, and Silverwing), while the dragon Morning was born the war itself. The last Targaryen dragon died in 153 ᴀᴄ, during the reign of King Aegon III Targaryen, who received the nickname “the Dragonbane” as a result, despite later attempts to hatch remaining eggs.
The dragon eggs and the nineteen dragons skulls of various sizes and ages were displayed by House Targaryen in the throne room of the Red Keep were all that remained of the dragons. Several Targaryen monarchs attempted to hatch the eggs over the years, some with disastrous results. Dragons are believed to be intrinsically tied to magic in the world, and indeed, it is said that the summers have become shorter, and the winters colder and crueler since the last dragon died. Archmaester Marwyn of the Citadel of Oldtown believes the secret goal of the order of maesters to be to suppress magic, and so blames them for the extinction of dragons. Read more...