A Game of Thrones prequel about House Targaryen is in the works, and here are the best stories HBO can use for the series. Arguably the most important house in Westerosi history, the Targaryens trace their history back to the Freehold of Valyria, before the Doom, and they not only united the Kingdoms of Westeros but ruled over them for hundreds of years as well.
Dragonriders, conquerors, and warriors, the Targaryens were some of the greatest men and women in the history of Westeros. However, they were also some of the worst. Madness, viciousness, and treachery runs through the history of this house as well, as evident by both Aerys II Targaryen aka the Mad King and Daenerys Targaryen aka the Mad Queen. As for the upcoming prequel, at the moment it still hasn't been officially greenlit, but it's rumored to be almost there - and it looks like it's going to involve dragons and Targaryens. However, as George R.R. Martin has written extensively about the history of House Targaryen, it's not easy to guess which particular corner of this lore is going to be the one explored in the upcoming series.
HBO could choose to go all the way back to the beginning, to Aegon's Conquest, or pull from more recent history, and even include some names that Game of Thrones fans will recognize from the mainline show. Whatever the decision, there are plenty of great stories to choose from that all involve the intrigue, romance, and dragons that fans of the show will want to see again.
Aegon's Conquest
Although the history of House Targaryen stretches further back than Aegon's Conquest, this is the start of uniting the Seven Kingdoms, and it would be appealing to fans of Game of Thrones. This would also allow for fans to stay on somewhat familiar ground, and explore the ancestry and houses of their favorite characters, as they react to Aegon's invasion. Focusing on Aegon's Conquest would show the Targaryens as a powerful house, and Dragonstone at its prime.
Dragonriders would also be a huge part of the series, as Belarion, Meraxes, and Vhagar are ridden in to take the Kingdoms - and it would be especially interesting to see the scale of the dragons; Belarion was enormous, far bigger than Daenerys' dragons (and bigger than any that came after him), which would be incredible to see with a proper budget. Aegon's Conquest as a series would also allow fans to see the Burning of Harrenhal, as Aegon destroyed it when King Harran Hoare refused to surrender, and it has only been seen as a blackened ruin of its former glory in the series. Finally, this choice would allow for fans to see the Iron Throne being forged (having now seen it melted), as well as seeing the founding of King's Landing.
There are a few issues with Aegon's Conquest, though. For one, it's far from a surprise ending. Game of Thrones fans know that Aegon was successful; however, there are plenty of smaller twists and turns that would keep any but the most devoted fan on the edge of their seat. It's also a good blend of the familiar and the unfamiliar, but it may not have quite enough political intrigue to match Game of Thrones in that respect. The Conquest is more battle-heavy than the earlier (and more popular) seasons of the show, which may mean that a series focused on it lacks what made Game of Thrones so powerful. The final issue with this is a more practical one. The cost of production on a show with multiple massive dragons and aerial battles might simply be too prohibitive.
The Origin Of Daenerys' Dragons
Another choice that would have some more direct ties to Daenerys Targaryen would be to explore the history of her own dragons - or more specifically, one particular story from the Targaryen vault that would trace her dragon eggs back to their origins on Dragonstone. This takes place around 50AC and is the story of Elissa Farman and Queen Rhaena Targaryen. Rhaena was the granddaughter of Aegon the Conqueror and was one of the six wives of King Maegor the Cruel.
The story of her marriage and the Black Brides itself would be a fascinating one for this prequel series, but the part of her life that related to Daenerys and her dragons comes after that time. When Rhaena was the ruler at Dragonstone, she was known as Queen in the East. There, she was happy to stay, but her best friend, Elissa Farman, one of her ladies, was increasingly bored. Elissa was desperate to leave and explore, but Rhaena refused to allow her to go. Eventually, Elissa took matters into her own hands; she stole three dragon eggs from Rhaena, and took off in the night. She made it to Braavos under the name Alys Westhill, where she sold the eggs to buy a ship, and sailed it away, seeking to discover what lay beyond the borders of the known world.
Choosing to make this story the focus of the Targaryen prequel would be a great way to tie the new series effectively to Game of Thrones, and to capitalize on the fan enthusiasm for an Arya Stark sequel series that would see her exploring across the sea. As Elissa Farman had the same desire to explore, she would be a phenomenal fan stand-in for Arya herself. This would also be a series focused more on politics and intrigue than war itself, which would be less costly (saving some money for the dragons themselves), as well as being predominantly female-led.
The Dance of the Dragons
The most likely story for the prequel series to cover is the Dance of the Dragons, the Targaryen Civil War that took place between 129 and 131 AC. Following the long rule of Jaehaerys and his son, Viserys, the Targaryens were strong - and there were simply too many of them. The right of the throne was in dispute, and while there were multiple contenders, the Dance came down to two sides - the Green and the Black. Aegon II and Rhaenyra were the principal contenders, with most of the houses of Westeros choosing one of their sides, but as the war continued, new possibilities arose.
The Dance of the Dragons is the obvious choice for the HBO show, largely because it is extremely similar to the story of Game of Thrones itself. Warring factions, marriages, intrigue, and major battles are combined in this war, but unlike Game of Thrones, there are significantly more dragons. Aerial battles between dragons, dramatic deaths, and the sight of House Targaryen at the height of its rule would make for an incredibly impressive series - and in this case, George R.R. Martin has already written the end, so there wouldn't be the issue of the storyline jumping the shark.
Of course, the similarities may also be the downfall of this as the choice for the prequel series. In many ways, Dance of the Dragons may simply not be different enough to appeal to people who watched their way through eight seasons of Game of Thrones. More dragons may make for more interesting viewing (and the storyline is simpler, not including the White Walkers), but they would also make production more expensive. There are also no clear and direct connections to the characters of Game of Thrones, yet there are dozens of players, and it may be nice to see a prequel series that isn't quite so complex.
The Blackfyre Rebellion, Jaehaerys, And More Possibilities
There are, of course, many more stories that come from Fire and Blood - not to mention from other companion books and George R R Martin's history of Westeros - that would make for good source material for a prequel. Should HBO choose to go with a more battle-driven story, the history of the Blackfyre Rebellions (another civil war, between Daeron Targaryen and his half-brother Daemon Blackfyre) would be a great choice. This would also see some more of Dorne in the prequel, as the Dornish at court were a driving factor in the civil war, and the Dornish didn't get quite the attention that they could have in Game of Thrones itself.
On the opposite end of the spectrum, the long and peaceful rule of Jaehaerys would be a great way to explore the Seven Kingdoms in a time of relative peace, something that Game of Thrones fans have yet to see. This doesn't mean that there would be no intrigue (this is a court, after all) but that the focus would be on more of the world and court itself, rather than massive bloody battle scenes. Or, rather than looking to Fire and Blood for inspiration, the new Targaryen prequel could draw from the series of novellas called The Tales of Dunk and Egg. These cover the time that Prince Aegon V Targaryen traveled the kingdom with Duncan the Tall, posing as his squire, Egg, and is something totally different - and as far from the pageantry of the court as it could be. All in all, there are plenty of Targaryen stories HBO could pull from for their new Game of Thrones show, but some of them are better than others.