Maybe it's a former soldier who has shown great courage during a battle. He could have been the one to hold the line at Moat Cailin during a crucial fight, and in recognition of his valor, he's made the new lord. His military experience would be a great asset in ruling the area.
There's also the possibility that it's a character from another region who has some connection to Moat Cailin. For example, a merchant who has been trading with the people there for years and has earned their respect. He uses his wealth and influence to become the new lord, bringing new ideas and a different perspective to the governance of Moat Cailin.
The new lord of Moat Cailin in fanfiction could be a great hero. He might use his position to improve the lives of the people there. He could start by strengthening the defenses of Moat Cailin, making it a more formidable stronghold. He may also establish trade routes, bringing prosperity to the area. This could attract more people to come and live in Moat Cailin, increasing its power and influence in the North. And he could form alliances with other noble houses, not just for military purposes but also for cultural and economic exchanges.
Perhaps a young knight who is given a lordship as a reward for his heroism in a great battle. He is inexperienced in ruling but has a strong sense of justice. He has to learn quickly how to manage his lands, deal with political intrigue, and protect his people from bandits and rival lords. He is also a bit of a romantic, and his love interest could be a lady from a neighboring house, which adds another layer of drama to his story.
One idea could be a new lord who is a long - lost heir to a powerful but fallen house. He starts from nothing, gathering a small group of loyal followers, some outcasts and misfits. He uses his wits and new - found knowledge of forgotten battle tactics to slowly rise in power. He might form an alliance with a group of local peasants who are tired of being oppressed by the existing lords. Through their combined efforts, they start to build a new, more just community which catches the attention of the greater powers in Westeros.
Well, it could be a character created by the fanfiction writer, perhaps a powerful mage who emerges from a long - forgotten land and claims god - like powers. This new god might bring a new set of rules and magic to the already complex world of Westeros.
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.
The Mother. In the existing lore, she is a major figure. In fanfiction, she could be more actively involved in the events of Westeros. She could be a guiding force, using her powers to heal the sick and wounded, and trying to prevent the bloodshed that is so common in the Game of Thrones world.
Perhaps it could be a character like Bran Stark. He has the power of the Three - Eyed Raven, which gives him access to a vast amount of knowledge and some control over time and events. It's not a far stretch to think that he could develop into a Master of Death in a fanfiction.
There could be a group of main characters. One could be an old maester who has seen many things during the previous era and now serves as a mentor to the younger generation. A second could be a wildling who has decided to integrate into Westeros society but faces many challenges. And a third could be a young noblewoman who is disillusioned with the traditional role of women in Westeros and is fighting for more equality. Together, they could be involved in all sorts of adventures and political intrigue in the new era of 'Game of Thrones'.
There could be a young mage named Lyra who has the power to communicate with animals. Her unique ability makes her a very interesting character as she can gather intelligence from all over Westeros through the animals she befriends.
One great 'Lord of the Rings and Game of Thrones Fanfiction' is 'The Convergence of Westeros and Middle - earth'. It combines the magic systems of both in an interesting way, like how the One Ring could interact with the magic in Westeros.