Dragons, Wyrms, and Wyverns: Their Unnatural History
Dragons, Wyrms, and Wyverns: Their Unnatural History, also known as Unnatural History, is an important text about dragons, wyrms, and wyverns, written by Septon Barth, the Hand of the King of Jaehaerys I Targaryen. Because Barth was considered more of a sorcerer than a septon by his enemies, copies of the book were burnt during the reign of King Baelor I Targaryen, and it is hard to find today.
In his book, Septon Barth considers various legends examining the origins of dragons and how they came to be controlled by the Valyrians. His theories include the speculation that the bloodmages of Valyria used wyvern stock to create dragons. This claim is considered highly dubious by most maesters.
Septon Barth also claims that dragons are neither female nor male, but shift sexes, "as changeable as flame". Barth further dispels the myth that a dragon can be slain by attacking down its gullet:
Death comes out of a dragon's mouth, but death does not go in that way.
A fragment of Unnatural History has proved controversial among maesters. Claiming to have consulted with texts preserved at Castle Black, Septon Barth stated that the children of the forest could speak with ravens and could make them repeat their words, and thus send messages over a great distance. According to Barth, the children taught this magic to the First Men, and this knowledge was passed down to maesters, but degraded, as they no longer know how to speak to the birds, but only send messages on parchment tied to a raven's leg. Most in the Citadel believe that ravens are incapable of true speech; a few maesters who specialize in the higher mysteries have argued that Barth was correct, but have not been able to prove it.
A Dance with Dragons
While writing his dragonlore, Tyrion Lannister recalls that ten years previously he had acquired a fragment of Unnatural History that had eluded Baelor's bookburnings. He doubts any of Barth's work had found its way across the narrow sea.
While enslaved outside of Meereen, Tyrion watches the Yunkish defensive preparations in the eventuality that Drogon should return. They are angling their scorpions and mangonels upward at the sky. Tyrion knows that they are wasting their time, and his thoughts turn to Barth's words about the futility of attempting to slay a dragon via its gullet.