Because of all the fan theories out there I decided to explain how I derive my own. This is specifically in the hopes that people will take mine more seriously than they have others.
First, let me explain why other fan theories fail. All too often the people making them take a few isolated details of the story and extrapolate from them. Not only has this led to vast numbers of theories, but also blatantly contradictory theories. Obviously they can’t all be right. In addition, they are also totally concerned with individual characters and often ignore how they impact the wider story. So I am going to lay out how I have developed my own theories and hopefully people will see the logic in them.
The easiest way to do that is to examine (F)Aegon Targaryen.
I do not think there is much question in anyone’s mind that Faegon is not the true-born son of Rhaegar. Not only does Varys’ story of his survival not make sense, but the vision Dany has in the House of the Undying clearly implies that he is the ‘Mummer’s Dragon’. The mummer, of course, is Varys. The primary, if indeed only, alternative that has been suggested is that Faegon is a Blackfyre, the family which attempted to supplant the Targaryens for a century. This is probable, as the Blackfyre Rebellions play a massive role in the backstory of ASOIAF.
That it is suggested that Varys is the brother of Faegon's mother, and therefore brother-in-law to Illyrio Mopatis, appears to be all but certain. This helps us to understand Varys' motives and explains his actions. He is actively working to weaken the kingdom and aid Faegon in taking the throne.
But the vision implies even more than that. Because it is included in the set referred to as ‘'Slayer of Lies’ it clearly involves Dany proving, or it being proved, lies or deception in the narrative. Obviously Faegon not being Rhaegar’s real son fits this description. But it can also be inferring something else. I noticed how each of the three sets of visions, Slayer of Lies, Bride of Fire, Daughter of Death, all have points in common. See the article on Dany's Visions 1.
The vision of Faegon appears not only in the row of ‘'Slayer of Lies’, but also in the column ‘'A False Future’. Each of the visions within this column involve events that are not going to happen. In this instance the false event is Faegon’s conquering Westeros. In the books Faegon is very likely to come close to capturing Kings Landing, but will fail, likely by being killed.
So what conclusions can we make? We must first consider other events that have also taken place within the story:
1)Arianne Martell has been sent by her father Doran to meet and, if possible seduce, Faegon.
2) Jon Connington, Faegon’s guardian and advisor, contracted grayscale, a notorious disease that inevitably drives its victims insane and then kills them.
3) Jon Connnigton, or Jon Con as he is known, was devoted to Rhaegar, being quite literally in love with him. Jon Con is a known homosexual.
4) The Blackfyres are the sworn enemies of the Targaryens and the Golden Company was formed by the Blackfyres specifically to fight the Targaryens.
5) As Tyrion discovers, as part of the plan of Ilyrio Mopatis and Varys, Faegon is supposed to marry Daenerys.
6) Robb Stark broke his engagement with the Freys to marry Jayne Westerling. Although his expressed reason was to protect her honor, it is reasonable to assume, as is shown in the show, that he was really looking for an excuse to get out of a deal he did not want.
7) Mace Tyrell, the bumbling idiot who rules the Reach, is marching toward Storm’s End.
8) Under Faegon’s leadership, and the advice of Tyrion, the Golden Company has seized Storm’s End.
9) Varys has confirmed by his own words that he is aligned with Faegon.
10) Doran Martell has attempted in the past to make an alliance with the remaining Targaryens. His efforts were less than exemplary.
11) Doran’s son Quentyn traveled to Meereen in an effort to consummate the alliance between the Martells and Daenerys. He subsequently was killed trying to steal one of her dragons.
12) The Sand Snakes have pledged to avenge their father.
13) The Lannisters are thoroughly hated by everyone in Dorne.
14) Cersei up to this point does not know the fate of Sansa Stark.
15) Sansa is in the Vale pretending to be the bastard daughter of Littlefinger named Alayne Stone.
16) Littlefinger is playing Cersei against the Tyrells in an effort to drive them apart. He is also responsible for starting the war between the Lannisters and Starks.
17) Although so far unrevealed, it is widely believed that Littlefinger’s ultimate objective is to put himself on the Iron Throne.
18) Littlefinger has repeatedly expressed his love for Catelyn Stark and for her daughter Sansa. How genuine this is, is questionable.
19) Littlefinger has pushed Sansa into marrying certain people who could advance his objectives: Joffrey Baratheon and Harrold Hardyng.
20) Littlefinger engineered the murder of Joffrey and will likely do so to Hardyng.
21) Sansa is, at this point in the book story, still enthralled by Littlefinger. The skepticism she exhibits in the show has not yet manifested itself.
So what is the conclusion from all this? Here is mine:
Mace will attempt to take Storm’s End and be defeated. It is widely believed that the battle for Meereen, the Battle of Fire, is the counterpart of Stannis' battle for Winterfell, the Battle of Ice. This is inaccurate. As shown in Cersei's article, the Battle of Fire is the counterpart of this battle, Mace's attempt to conquer Storm's End. Both are efforts to end sieges against overwhelming odds. And just as Barristan will win an unexpected victory outside of Meereen, Faegon will win an equally unexpected victory here. Also for the same reason, incompetent leadership among their enemies.Mace’s army will be routed and Faegon will make a triumphal march to Kings Landing with the Golden Company.
Arianne will join up with Faegon and successfully seduce him.
This is where Robb’s wedding comes in. Most people don’t understand what true foreshadowing is. It is not just some random word or phrase that just happens to hint at a future development. Nor does the saying ‘history does not repeat, but it does rhyme’ mean that future events copy previous events point-by-point. Robb’s wedding, and the subsequent aftermath, is foreshadowing of Faegon’s fate as well as being a main event in its own right. Faegon will marry Arianne using the exact same excuse Robb used to marry Jayne, to ‘protect her honor’. As with Robb, this is questionable. Regardless, it will have catastrophic results.
Faegon’s marriage will likely take place right before the Golden Company marches into Kings Landing. Varys will reveal himself as he tries to subvert the City Watch. The Watch is the only force left defending the city due to Mace’s defeat.
Thus, Faegon is on the cusp of winning it all. But the act is premature. To compound the mistake, he openly declares himself a Blachfyre, presenting as proof his possession of the sword Blackfyre.
Jon Con, who has devoted his life to Faegon under the belief that he is Rhaegar’s true-born son, will be driven over the edge. The grayscale is already going to drive him mad and the revelation of Faegon’s true parentage plus his jilting Dany by marrying Arianne will be the breaking point. He will murder Faegon and Arianne, likely screaming ‘for Daenerys’ while he is doing so.
The sudden death of Faegon will have massive ripple effects throughout the story. Not only in the immediate, but long term.
With Faegon’s death Varys will be betrayed by the City Watch. Cersei will then have him executed for treason. We cannot take too much from season 8 of the show, but in this one instance I think we can reasonably guess that Varys’ death is one of the things GRRM gave to Dan & Dave.
The phrase ‘for Daenerys’ is likely going to cause Doran to turn on the Targaryens. He was never much of an ally to begin with. He really was just a schemer and the death of both his eldest son and his daughter by those he would consider aligned with Daenerys will cause him to join with Cersei. This will cause the Sand Snakes to turn on Doran. They will justifiably consider him a back-stabber. They will murder him and also Trystane and Myrcella. Now, it is possible that Tyrstane and Myrcella will be murdered before the death of Faegon and Arianne. Once Arianne becomes wedded to Faegon her previous plan to make Myrcella queen will become a liability. But due to the pace of events I think it is more likely that Myrcella’s death will happen after Doran has a chance to reach an agreement with Cersei.
This is not the end of it. I like how Martin has arranged it so that all three of his ‘big schemers’, Littlefinger, Varys, and Doran, would all be undone by the same event. Schemers inevitably fall foul of their own schemes. At least we would like to think so.
That is the case here. Littlefinger gets great credit for being a genius puppet master who sets events into motion years before fruition. Credit where its due and all, no one is THAT good. Littlefinger is at heart a master manipulator who is an opportunist. He takes what comes along as he did when Catelyn showed up in Kings Landing with the Catspaw Dagger.
That is the case with Faegon. With the understanding that Littlefinger’s ultimate objective is to put Sansa on the throne with him by her side, he first tried to engineer a marriage between her and Joffrey. When Tywin, wittingly or unwittingly, spoiled that by having Joffrey marry Margery, he is now in the process of getting her to seduce Harry Hardyng. Given that his plan is likely to take years to come to fruition, the chance to cut short the wait is almost certainly going to be irresistible.
When Faegon is on his winning streak Littlefinger is going to offer him marriage to Sansa. When Faegon is murdered Littlefinger’s correspondence with him will become common knowledge, as will his sheltering of Sansa. This will destroy his links with Cersei completely. Just as Robb’s wedding and murder foreshadowed Faegon’s, so Joffrey’s wedding and murder also foreshadows Faegon’s. Martin loves to do things in 3's.
This will not result in Littlefinger’s death just yet, although it could. I believe his story still has some more to go, specifically him trying to use Sansa to gain control of the North. But it will be the beginning of the end. Not only will he be betrayed to Cersei, but his entire nature will be revealed to all. Thus destroying any chance he has to manipulate anyone else. More importantly, it will destroy Sansa’s faith in him and ultimately lead to her having him killed.