In a 'Harry Potter King of Essos' fanfiction, it could start with Harry feeling out of place in the wizarding world of Britain after the defeat of Voldemort. He then hears of Essos and decides to explore. Once there, he realizes the people are in need of a just leader. He starts to build his influence using his magical abilities. He forms alliances with different groups, from powerful mages to common folk. As he gains more and more support, he is declared the King of Essos. He then sets about reforming the magical society there, using his knowledge of Hogwarts' systems.
Well, one possibility could be that Harry Potter, through some magical accident or powerful spell, is transported to Essos. There, he discovers a whole new world of magic and politics. Maybe he uses his skills learned at Hogwarts to rise to power and becomes the King of Essos. He could introduce some of the wizarding concepts from his own world, like the use of wands or the sorting hat system, to the people of Essos.
The story could start with Harry accidentally ending up in Essos. He discovers that the magic there is different in some ways from what he's used to in the wizarding world of Britain. He might encounter new magical creatures and spells. As he tries to find a way back home, he gets involved in the local conflicts and starts using his unique magic, like the ability to speak Parseltongue, to his advantage and gradually conquers the challenges in Essos.
One main antagonist could be the existing power - hungry rulers in Essos. They would see Harry Potter as a threat to their rule and try to eliminate him. Another could be dark magic cults in Essos that oppose any form of new leadership or change that Harry might bring.
Potential characters could include Harry Potter, of course. Then, there might be some Essos warlords who are intrigued by Harry's magic. And we could see some characters from the magical schools or hidden magic societies in Essos. There might be a young Essos girl or boy with great potential in magic who Harry takes under his wing, similar to how he mentored some of the younger students at Hogwarts.
Well, perhaps in this fanfic, Harry Potter discovers some long - lost connection to Russia. Maybe he's the heir to a powerful Russian wizarding family. He could use his magic in a unique way influenced by Russian magic traditions, like using spells related to Russian folklore creatures.
Perhaps in this fanfiction, Harry Potter becomes the King of Gringotts due to some prophecy or a special gift he has. As the king, he could start to reform the goblin - wizard relations. He might introduce new policies in Gringotts that benefit both wizards and goblins, which would lead to a whole new set of adventures and challenges as he tries to balance the different interests.
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.
Maybe Harry discovers he has some hidden connection to Atlantis. He could be magically transported there and due to his powerful magic and heroic nature, he ends up becoming the king. He then has to deal with Atlantis's internal politics and protect it from external threats.
One possible plot could be that Harry discovers he has some long - lost royal blood. He then has to navigate both the wizarding world and the political intrigues of the English court as he tries to balance his newfound status as a potential king. Magic could be used to solve problems within the monarchy, like protecting the king from dark magic threats.
Well, perhaps Harry discovers he has some hidden power that is related to King Ghidorah. Maybe he can transform into King Ghidorah - like form in times of great danger at Hogwarts, using his new - found abilities to protect the school from dark wizards. The other characters would be both amazed and a bit scared of this new Harry.
One possible plot could be that Harry discovers he has a hidden connection to the vampire world and is actually the heir to the 'King of Vampires'. He then has to balance his life at Hogwarts with his newfound vampiric identity, facing challenges from both the wizarding world that may fear him and the vampire world that may have its own power struggles.