A possible plot could be centered around a Skagos native who has a prophetic dream about the future of Westeros. This person then embarks on a journey to find someone who can interpret the dream correctly. Along the way, they encounter various characters from the 'Game of Thrones' series and get involved in their own mini - power struggles, all while trying to fulfill their quest related to the prophetic dream.
One idea could be exploring what would happen if a minor character like Gendry had been secretly trained in magic. He could use his newfound powers to unite the smallfolk against the warring nobles. Another plot could revolve around a female knight from the North who disguises herself as a man to fight in the wars, and along the way, she discovers secrets about the White Walkers that no one else knows. Or perhaps a fanfiction where Daenerys and Sansa form an alliance much earlier and together they reshape the power dynamics of Westeros.
One idea could be exploring what would happen if a minor character, like Gendry, had a more central role in the fight against the White Walkers. He could lead a group of common folk and prove that the power doesn't always lie with the nobles.
A really cool 'Game of Thrones fanfiction' plot could involve the resurrection of some of the dead characters in a different way. For example, what if Ned Stark was brought back not as a vengeful wraith but as a wise advisor to a new king or queen? His honor and wisdom could shape the future of Westeros in a completely new direction. And it would be interesting to see how the other characters react to his return.
Perhaps a fanfiction where Daenerys Targaryen lands in Westeros earlier and forms an alliance with the Starks before the events of the main series. This would completely shift the political landscape and the fight for the Iron Throne. She could bring her dragons to help fight the White Walkers from the start.
One idea could be exploring what would happen if a minor character, like Gendry, became the King of Westeros. He has a claim to the throne through his Baratheon blood and his time with the Brotherhood without Banners could give him a different perspective on ruling. Another plot could involve a female character, like Brienne, leading a new order of knights that are dedicated to protecting the realm in a more democratic way. Or perhaps a story where the White Walkers and the humans form an uneasy alliance against a new, even greater threat from Essos.
One idea could be the Hound's journey after leaving King's Landing. He could encounter a group of outcasts and form an unlikely alliance to protect a small village from raiders. It would show his growth from a bitter, angry man to a more empathetic protector.
In Spartan Game of Thrones fanfiction, a possible plot is the discovery of Spartan artifacts in Westeros. A young maester finds a hidden vault with Spartan weapons and armor. He tries to understand their purpose and power. Meanwhile, a knight from a minor house gets hold of one of the Spartan swords. With it, he gains an edge in combat and becomes a key player in the power struggles, attracting the attention of the major houses and changing the course of the political and military affairs in Westeros.
One idea could be a character from a minor house rising to great power through unexpected alliances. For example, a character from House Frey who tries to redeem the family's name after the Red Wedding by allying with the Starks and helping them take back Winterfell. This would bring a new dynamic to the story as the character has to face the prejudices against their house.
Maybe a plot where a powerful noble is on his deathbed. He has lived a life full of sin and is terrified of facing The Stranger. He hires a group of mages to try and cheat death by warding off The Stranger. This sets off a battle of magic and wills, with the mages using all their knowledge against the unfathomable power of The Stranger. Meanwhile, his family members are divided on whether to support the noble's attempt or accept his fate.
Another plot could revolve around an emperor who is not from Westeros originally. Maybe he comes from a far - off land with different customs and magic. He tries to impose his own rules on Westeros while also having to deal with the resistance from the local lords. This could lead to a lot of interesting cultural clashes and power struggles within the story.