In a fanfiction, Hulk might be a part of a prophecy. The old seers could have foreseen his arrival in Westeros. Some would see him as a savior, while others as a destroyer. His actions could then be guided by the various characters trying to either fulfill or prevent the prophecy. For example, the Red Priests might think he is a tool of their god and try to manipulate him into doing their bidding, while the more skeptical characters would try to stop him from being used in such a way.
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.
The Hulk might be seen as a sort of monster in the context of Game of Thrones. Just like how they have direwolves and dragons, the Hulk could be another mythical - but in this case, suddenly very real - creature. He could be shunned by some and perhaps worshipped as a god by others, depending on how different regions of Westeros react to his existence.
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.
The Hulk would probably have a very different dynamic with the various characters. With the more honorable characters like Ned Stark, they might initially be cautious but then try to reason with the Hulk or at least figure out how to co - exist with him. However, with more power - hungry characters like Cersei, she might see the Hulk as a threat to her rule and try to eliminate him.
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.
His role could be that of a disruptor. Sasuke has always been one to go against the norm. In a Game of Thrones setting, he would likely not follow the traditional rules of Westerosi society. He might be a lone wolf, working towards his own goals while everyone else is vying for the Iron Throne.
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.
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.
He could play the role of a master strategist. Thrawn's ability to analyze his opponents and predict their moves would make him a valuable asset to any side in the 'Game of Thrones' power struggles. He could be the one to turn the tides in battles and sieges.
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.
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.