He might become a powerful wizard in Westeros. He could use his magic to fight against the White Walkers. His magical abilities would be quite unique in that world full of knights and swords.
Some characters in Westeros might be very suspicious of Harry. His strange clothes and the way he does magic would make them think he's some sort of dark sorcerer. Others, like the more open - minded ones, might be curious and want to learn from him. For example, Tyrion Lannister might see Harry as an interesting oddity and try to figure out how his magic works.
The fem Harry Potter could also change the power balance. If she aligns herself with a particular house, that house would gain an edge. Her knowledge of magic could be used to uncover secrets in Westeros, like hidden passages in castles or ancient prophecies that were previously unknown. This new information would disrupt the existing plans of the different factions vying for the Iron Throne and other power positions.
In fanfiction, 'Harry Potter changes Westeros' could be through his magic skills. For example, his spells like Wingardium Leviosa could be used to move heavy objects in Westeros, which might change the way battles are fought or construction is done. His knowledge of the magical world could also introduce new concepts to the people of Westeros.
One possible plot could be that Harry Potter, through some magical accident or powerful spell, is transported to Westeros. He might use his magical abilities to quickly rise in power, perhaps by impressing the local lords with his feats of magic. He could then set out to unite the kingdoms under his rule, using a combination of wizardry and political savvy that he learned from his time at Hogwarts and in the wizarding world.
In fanfiction, Harry and Kreacher could be seen exploring the different terrains of Westeros. Maybe they stumble upon the Iron Islands. Kreacher could be fascinated by the Ironborn way of life while Harry tries to find a way to use their naval power for some greater good. Or they could end up in King's Landing and face the political intrigue there.
Well, in this fanfiction, perhaps Harry Potter could use his magic to outwit the political intrigues of Westeros. He might introduce new forms of magic that could change the power dynamics among the houses.
A major impact would be on the economy. In the Harry Potter world, there are unique magical items and potions that could be introduced to Westeros. For instance, the Felix Felicis potion could be used by merchants to have good luck in their business dealings. This would change the way trade is conducted. Also, the introduction of magical beasts like hippogriffs could be used for transportation, which would revolutionize the travel and delivery industry in Westeros.
In a 'Harry Potter Lord in Westeros' fanfiction, the plot could center around Harry Potter becoming a lord in Westeros through some magical means. As a lord, he would have to deal with the typical issues like managing his lands, protecting his people, and forming alliances. However, his magic would give him an edge. He could use spells to improve the harvests, defend his castle from invaders more effectively, and even try to bridge the gap between the different houses by using his unique perspective from the wizarding world.