It could also be Littlefinger's followers or remnants of his schemes. Since Littlefinger had his own plans involving Sansa, his influence might still linger in fanfiction, and those who were loyal to him could oppose Sansa and Theon's attempts to bring stability to the North.
One interesting storyline could be Sansa and Theon teaming up to take revenge on their common enemies. They've both been through so much in the original series, and in fanfiction, they might use their combined knowledge and skills to outwit those who wronged them.
I really like the fanfic 'A Song of Rings'. In this story, the One Ring somehow finds its way to Westeros. The author does an amazing job of integrating the different lore. For example, how the power of the ring affects the power - hungry characters in 'Game of Thrones' is fascinating. It also shows how the characters from Middle - earth would react to the more brutal world of Westeros.
The 'forbidden love' trope can be really engaging. Imagine a love story between a character from 'Game of Thrones' and one from 'Lord of the Rings' in a crossover fanfiction. This trope can create a lot of conflict and emotional depth. And the 'rag - to - riches' or 'rise to power' trope is also seen a lot, as it shows the character's growth and transformation.
Well, the Lord Beyond the Wall might be a figure who has been there since the dawn of time in the fanfic's version of the 'Game of Thrones' universe. Maybe he's a spirit or a long - lost hero who has turned into something more due to the magic and harshness of the far north. He could be a force that both the Night's Watch and the wildlings fear or revere, depending on how the story in the fanfic unfolds.
The biggest challenge is probably the different magic systems. In 'Lord of the Rings', magic is more ethereal and associated with certain races. In 'Game of Thrones', it's more of a mysterious and often dark force. Combining these two concepts without making it seem forced can be difficult.
Power struggle is a very common theme. Just like in the original series, the OC lords in these fanfictions often strive for more power, whether it's over a particular region or in the whole of Westeros.
First, know the source material well. Understand the characters, their motives, and the world - building of both 'Game of Thrones' and 'Lord of the Rings'. Second, create unique and interesting crossovers. For example, how would the One Ring affect the power struggle in Westeros? Third, focus on character development. Let the characters grow and change in new and unexpected ways.
One way could be by having characters from 'Lord of the Rings' appear in the 'Game of Thrones' world. For example, Aragorn could show up as a mysterious ranger in the Seven Kingdoms. He might use his skills to navigate the political intrigue and power struggles, much like he did in Middle - earth.
One interesting crossover could be the characters from both universes meeting in a magical realm. For example, Aragorn from 'Lord of the Rings' and Jon Snow from 'Game of Thrones' might team up to fight a common enemy like a powerful dark wizard. Their different combat styles and leadership qualities would make for an exciting story.