Speculations on A Song of Ice and Fire
Blood, Fire, and Magic
The Targaryen Dynasty
Why was Aegon the Conqueror? Was it personal? Or did prophecy have something to do with it?
We are given no information on Aegon's ancestors beyond Daenys the Dreamer and her daddy who relocated the family to Dragonstone. The choice of Dragonstone is telling, not only regarding the Conquest, but because Dragonstone is a massive reservoir. The island is practically made of dragonglass. And is an extinct (?) volcano. The significance of this will be explained later.
It has to be because Aegon had such powerful magic blood. That the Prince that was Promised was to have been a scion of the Targaryen family seems beyond question. The reasons for why has been related in the articles on the weirwoods and the Others. We have no evidence as yet which Targaryen member Aegon and his sisters believed to be the Prince. We can assume that they did not grasp just how long a time would pass before the Prince was born.
Over the course of the Targaryen rule of Westeros the path of the dragonrider trait can be traced through the generations from Aegon himself to Dany and Jon.
Aegon I (The Conqueror) + (Rhaenys) - Aenys I - Jaehaerys I (The Conciliator) + Alysanne - Baelon + Alyssa - Viserys I? - Rhaenyra + Daemon - Viserys II - Aegon IV (The Unworthy) + Naerys - Daeron II - Maekar - Aegon V (The Unlikely) - Jaehaerys II + Shaera - Aerys II (The Mad King) + Rhaella - Daenerys/Rhaegar - Jon (probably Jaehaerys III in the books)
+ indicates an incestuous marriage wherein in is indeterminate which sibling or both contributed.
Certain points need to be stressed. We frequently cannot tell whether the blood passes through the father or the mother, or even if both has some kind of amplifying affect. Viserys I was barely a dragonrider and Balerion was dying by that point. Yet all his children and grandchildren bonded with dragons with a couple of exceptions.
This actually brings up an interesting point. We don't know if his children inherited the trait from him or his wives. Both his wives almost certainly had Targaryen blood:
Daella Aemma Rhaenyra
Saera Alicent Aegon II
This supports the contention that the trait passes primarily through the mother.
Viserys II never bonded with a dragon. (On a side note, notice that all the Targaryens named Viserys are not dragonriders, not really.) But we don't know if that's because he spent years away from his family and when he returned they were mostly dead. The people's belief in the Tararyens was severely weakened. Plus, he spent very little time on Dragonstone.
The importance of this will soon become apparent.
It would be easy to assume that after the death of the dragons the trait was gone too. Yet there are signs that the trait was very much there. Aegon IV's health problems have been chalked up to his lifestyle. But the effect on his body at his death bares more than a passing resemblance to Targaryen stillborns. Aegon V, Daeron II, and Jaehaerys II might also show signs of having it.
If we go with the presumption that the trait is weakened, if not gone altogether, the question then becomes what brought it back? It goes without saying, Targaryens are not the only ones who have magical bloodlines. Aegon V married a Blackwood. The Blackwoods like the Starks are of the North with strong ties to the Children of the Forest. Maekor married a Dayne. As explained in my speculations on the original Long Night, Eldric Dayne married a woman who belonged to the ancient ancestors of the Valyrians. The possibility exists that Viserys II's wife might have had some of it, for the people of Lys are of almost pure Valyrian stock. The incestuous marriages that came after Aegon IV also increased whatever trace of the trait remained in the bloodline.
The marriage of Rhaegar and Lyanna gives Jon a true mix of the two magic bloodlines in the story: the dragon and the wolf. It is not an accident that Dany and Rhaegar's parents were brother and sister. Lyanna was pure Stark. It is also not an accident that her parents were cousins once removed. This alone would be enough to prove Jon is the Prince that was Promised even if there weren't any other clues.
Fire and Blood
The Targaryen House words.
We have gone over the importance of blood to magic and the casting of spells. But there is another element that is equally important - fire.
On Planatos magic usage is separated into the elemental forces much as the ancient Greeks would have recognized: air, earth, fire and water - aeromancers, terramancers, pyromancers, and aquamancers.
There might also be a separate school for spirit - animancers. There is certainly one for the dead - necromancers.
I don't know which of these schools blood magic would fit into for it appears to cross into all of them to some degree.
Of all the schools the one of fire appears to be most common. This is likely just because it is the most popular.
We have no evidence that any one school is more powerful than another. Though we have not heard anything about terramancers and animancers. Aeromancers are only mentioned. There are stories about aquamancers and necromancers in the World Book.
The power of fire needs no explanation. Fire represents life. The central nature of fire to the religion of R'hllor is explained in the Melisandre article. What needs to be explained now is how fire connects with magic.
Fire doesn't create magic, nor does it store it. Rather, magic flows through fire. This might help to explain why fire is popular as a medium for magic.
Unlike fire, all the other elements have a physical dimension. Unless you count spirit as an element, which I don't. Given that magic flows so readily through fire it doesn't absorb any magic energy as all the other elements do. Like using a metal pan. Copper transmits heat more readily than iron, but it also absorbs less of it.
As explained previously, magic flows like water and the elements of the world carry it. Places where elements concentrate is also locations where magic accumulates. This might help explain why some places become reservoirs and others don't. Targaryens have dragonblood or fire in the blood. Dragons are fire made flesh. The Wall is made of ice, frozen water. The greatest river on Planatos is the Rhoyne.
Dragonstone ranks as one of the greatest reservoirs of magic on Planatos. It is a concentration of all the elements put together. Dragonglass - frozen fire. An island soaked with storms - water and air. It is also a volcano, the often ignored element of earth - terra. This would explain why Aenar settled his family there. Earth stores magic more than any of the other elements, which is no doubt why we don't hear about terramancers in the lore.
Winterfell is another location of concentrated magic. Steam from its underground geysers is water and fire. It is frequently exposed to snowstorms even during the summer. Water and air. And I'm betting that there is dragonglass hidden deep within the crypts.
Winterfell lacks the concentration of earth like Dragonstone. Dragonstone, having concentrations of both fire and earth is ideal.
The most visible effect of this is that dragons are more likely to hatch on Dragonstone than anywhere else. When combined with Targaryen blood dragons grow both faster and larger than anywhere else.
This calls into question the wisdom of Aegon's conquest. If speculation about Aegon's motives are accurate, the Targaryen conquest took place three hundred years too early. It is very possible that Aegon conquered Westeros in order to unify it to face the enemy that was going to destroy them. It also raises the possibility that the weirwoods are responsible for Aegon's conquest just as they are responsible for the War of the Five Kings. Visions from the weirwoods could indeed be responsible for Littlefinger engineering the war. Their motive for doing so is of course to weaken Westeros for the invasion of the Others.
Conclusion
Wrestling with this article I have constantly wondered how this ultimately effects understanding of the story. Does it change my interpretation of it? Probably not. I have grasped in a general sense how Martin was using magic for a long time. But his avoidance of any explanation of it shows that he is ambiguous himself as to how it effects his world and its significance. In the end, the magic of ASOIAF is not meant to override the underlying themes. Rather to enhance them. What is perhaps most important, particularly regarding how people expect the ending to go, magic is never going to disappear from Westeros. It is as permanent as the weirwoods and will only die when they do. The life or death of the dragons makes no difference.