Daenerys might also be affected. If word reaches her that Oberyn has won and is making changes in Westeros, she might see an opportunity to form an alliance with him. She could offer her dragons and her army in exchange for a share of power in Westeros. This could lead to a very different endgame for the series, with multiple powerful players working together or against each other in new ways.
Robb winning the war in the fanfic might be due to his ability to gain more support from the common people. If he promised fairer rule and actually delivered on it, more people would be willing to fight for him. He could also have some unexpected help, like a powerful but previously unknown group coming to his aid.
The characters' fates would be drastically different. Daenerys might not have to go through all the hardships she faced in the original story as she could grow up in a more stable Targaryen - ruled Westeros. Tyrion could find himself in a court that values intelligence more, given Rhaegar's own intellectual pursuits.
If Rhaegar won in a 'Game of Thrones' fanfic, perhaps he could have restored the Targaryen dynasty to its former glory. He might have been able to bring about a more peaceful reign, with his love for music and the arts influencing the court. He could also have made different alliances, changing the political landscape of Westeros completely.
It would change the storyline drastically. For one, many characters who died in the original story might survive. Robb's victory could mean a different fate for Sansa and Arya, as he would have more power to protect his family. Also, the political landscape would be very different. The Lannisters would be in a much weaker position, and that would affect how they interact with other houses.
If Robb won the war in a fanfic, it could lead to a completely different Westeros. He might establish a more just rule in the North and perhaps even expand his influence over other kingdoms. Maybe he'd form new alliances and bring about an era of peace and prosperity, unlike the chaos that followed in the original series.
If Rhaegar won in the 'Game of Thrones' fanfic, perhaps the Targaryen dynasty would be restored to its former glory. He might bring about a more just rule, with less bloodshed compared to the chaotic events that unfold in the original series. He could also potentially reunite the Seven Kingdoms under one banner more peacefully, using his charm and leadership skills.
There is a fanfiction called 'Oberyn's Quest'. It follows Oberyn on a journey across Westeros where he uncovers some long - forgotten secrets. The story does an excellent job of staying true to his character, his determination and his cunning nature, making it a great read for Oberyn Martell fans.
In a fanfic, if Oberyn wins, he may also decide to take Sansa Stark under his protection. He could see her as a key to future political stability. With Sansa in Dorne, he could use her claim to the North to form a coalition against the Lannisters, uniting the North and Dorne against their common enemy.
Well, if Rhaegar wins in this fanfic, Arya Stark could be a sort of diplomat for the North. Rhaegar would need to keep the North in line, and Arya, being a Stark, has the influence to do that. She might also befriend Rhaegar's family, like his sister or wife if he has one. Her journey could change from seeking revenge to building a new world under Rhaegar's rule. Maybe she'd even teach some of Rhaegar's men her unique skills, making them better fighters and spies.
The Blackfyre can have a huge impact on character development in fanfiction. For example, a character who was previously uninterested in power might become consumed with the idea of ruling once they get involved with the Blackfyre. It can also create moral dilemmas. Should a character support a Blackfyre claimant, knowing it might lead to war? Or should they stay loyal to the existing regime? These questions can shape a character's journey and decisions, which in turn influence the overall plot of the fanfiction.