He could be a powerful sorcerer from a far - off land who arrives in Westeros. Maybe he uses his magic to manipulate the power struggle, secretly siding with different houses to further his own mysterious goals.
In a 'Game of Thrones' fanfiction, Loki could be a fallen god seeking redemption in the brutal world of Westeros. He might initially try to use his powers for his own gain, but as he witnesses the suffering and the complex web of politics, he starts to side with those who fight for justice. He could use his otherworldly knowledge to help the Starks or Daenerys in their quests, while also trying to atone for his past misdeeds.
He might ally with Arya Stark. Loki would see her determination and skill, and they could form an unlikely partnership. Arya could learn some new tricks from Loki's magic, and Loki could use Arya's knowledge of Westeros to his advantage.
He could be a major villain. His ambition and power - hungry nature would fit right in. He might seek to rule over all the kingdoms in Westeros, using his dark magic to eliminate any who oppose him.
Dracula could be a powerful antagonist. He might be seeking to rule Westeros or just cause chaos for his own amusement. His powers would make him a formidable foe to the various houses vying for the Iron Throne.
The Dovahkiin could be a protector in a Game of Thrones fanfiction. With their great strength and powers, they might safeguard the innocent from the horrors of war, like the smallfolk who are often caught in the crossfire in GOT. They would not side with any particular house just for political gain, but rather help those in need.
They could be traders. Bringing unique goods from their own lands, like fine wines, silk, or advanced metalwork. Their arrival could disrupt the existing trade routes and economies in Westeros.
Hulk could be a protector of the Wall. Instead of the Night's Watch, he stands guard against the White Walkers. His strength would be a great asset against the undead hordes. He might not understand the politics of the Seven Kingdoms, but he knows when something is a threat. And the sight of a giant green monster fighting off the White Walkers would be an amazing addition to the Game of Thrones lore. He could also form an unlikely friendship with some of the members of the Night's Watch, like Jon Snow, who would respect his power and his simple sense of right and wrong.
He could be a disruptor. His modern - day technology and ideas would go against the traditional ways of Westeros. For example, he might try to abolish the feudal system with his democratic ideals.
Jon could also be a mentor figure. After learning the ways of the Jedi, he could teach others, especially those from Westeros who might also have hidden Force - sensitive abilities. His experience in both worlds would give him a unique perspective to pass on to his mentees.
Tom Riddle might be a manipulator. He could play different houses against each other. For instance, he could convince the Lannisters that the Starks are planning something against them, and then do the same to the Starks about the Lannisters. His goal would be to create chaos so that he can rise to power in the resulting turmoil. He has the intelligence and the deviousness to pull off such schemes.
In this fanfiction, Naruto Sage could become a mentor figure. He has a lot of knowledge and skills that could be passed on to the characters in Westeros. He could teach them about discipline, as he was trained rigorously in the ninja arts. Also, his sage mode gives him insights that could be useful in understanding the magic and mysteries of Westeros. For instance, he might help Bran understand his new powers better. He would be like a strange, yet powerful, new addition to the already diverse cast of characters in GoT.