One consequence could be a shift in the power balance. The Mountain was a powerful fighter in service of certain lords. His death would leave a power vacuum among his allies. Robb Stark, on the other hand, would gain more notoriety. His reputation as a fearsome and capable leader would spread, making his enemies more cautious of him.
There could be revenge attempts. The Mountain had his own followers and those who supported him. They might seek to avenge his death by targeting Robb Stark or his allies. This could lead to more battles and bloodshed in the fanfiction world. Also, it might change the political landscape as different factions would start to realign themselves based on this new development.
Well, in the fanfiction world, Robb Stark might also get some unexpected help. Maybe there are some magical elements involved. A wizard or a sorceress could weaken the Mountain's strength or defenses. This would give Robb an edge in the fight. Then, with his courage and fighting skills, he could step in and slay the Mountain.
The Old Gods themselves would be crucial. They could be represented in various forms like the weirwood trees. And there might be some sort of priest or seer who serves as an intermediary between Robb and the Old Gods, guiding him through the spiritual experiences.
It could lead to a major shift in the power dynamics of the story. Maybe it would prevent the Red Wedding or cause other unforeseen conflicts.
One common theme is leadership. Robb Stark is a leader, so many fanfics explore how he leads his men, makes strategies, and deals with political situations.
Well, if Robb Stark wins the war in the fanfiction, he would likely have a major impact on the political landscape. He could reshape the power dynamics, perhaps even expanding his influence beyond the North. He might also be in a position to avenge his father's death more thoroughly and bring stability to the realm. Additionally, his victory could lead to different character developments for those around him, like his mother or his bannermen.
One possible plot could be that Robb Stark manages to avoid the Red Wedding trap. Maybe he receives a tip - off from an unexpected source, like a disgruntled Frey servant. With this knowledge, he could turn the tables on his enemies. He might use his military strategy skills to ambush the Freys instead, and this could lead to a major shift in the power dynamics in the North, with Robb emerging as an even stronger leader.
Well, in this fanfiction, Robb Stark might experience a spiritual awakening. He could be guided by the Old Gods, perhaps receiving visions or prophecies that would change his course of action in the war. Maybe he'd find ancient wisdom that gives him an edge against his enemies.
A possible plot could be that Rhaenys and Robb meet by chance, and despite the initial shock of their different backgrounds, they fall in love. Their marriage then becomes a symbol of hope for a more united Westeros. They might have to overcome the objections of their families and the political unrest that such a union could cause. It could also involve them learning about each other's traditions and forging a new path for their combined houses.
One possible plot could be that after the marriage, Robb Stark has to deal with the complex Frey politics. He might try to use the union to strengthen his position in the North. Maybe he and his Frey bride gradually fall in love despite the initial political motives of the marriage.
A sense of adventure is also present. They were in the middle of a war - torn Westeros. Fanfictions might take them on different adventures together, away from the main battles, or they could be involved in secret missions that test their relationship. Also, the theme of loyalty, both to each other and to their respective causes, is explored. How they balance their loyalty to each other with their loyalty to their families and kingdoms is a rich area for fanfiction writers.