One possible plot could be that Harry, through some magical accident or powerful spell, is transported to the world of Cintra. There, he discovers the danger it's in. Using his magical skills like the Patronus charm to ward off dark creatures threatening Cintra, and his knowledge of spells to help in battles. He might also form alliances with the local warriors, teaching them some basic magic for self - defense.
In a 'Harry Potter Saves Cintra' fanfiction, Harry could be summoned there by a powerful magic user in Cintra who has heard of his deeds. Once in Cintra, Harry realizes that the magic there is different but still manages to adapt. He teams up with a group of rebels who are fighting against an oppressive regime. Harry uses his magic to perform feats like creating large protective barriers around the rebels' hideouts. He also uses his ability to communicate with snakes (Parseltongue) to gain an edge in certain situations and ultimately saves Cintra from the tyranny.
Well, perhaps in this fanfiction, Cintra is facing a threat from an ancient evil. Harry Potter, with his Gryffindor courage, arrives. He first tries to understand the political and magical situation in Cintra. He then uses his invisibility cloak to gather intelligence. Eventually, he uses his powerful magic, like the Unforgivable Curses if necessary (though he hates them) to fight off the main villain and save Cintra from destruction.
It could be a dark wizard who has his eyes on Cintra's powerful magical artifacts. He wants to use them to gain more power and is willing to destroy Cintra to get them.
In this fanfiction, perhaps the centaur is in a situation where it's about to be sacrificed in some dark ritual. Harry discovers this and races against time to stop it. He calls upon his friends Hermione and Ron for help. Hermione uses her vast knowledge of magic to figure out how to break the dark magic circle, while Ron provides some much - needed comic relief during the tense situation. Harry, of course, is the one who ultimately uses his powerful Patronus charm to dispel the dark forces and save the centaur.
Well, perhaps Zoe is in danger from dark wizards. Harry, with his skills and bravery, could use spells like Expelliarmus to disarm the villains threatening Zoe. He might also use his invisibility cloak to sneak up on them.
The fanfiction could show that Harry discovers a secret passage that leads to where Cedric is held captive. He has to face various magical traps and challenges on the way. Once he reaches Cedric, he uses his Gryffindor courage and his knowledge of magic, like the Shield Charm to protect Cedric from incoming spells, and then they escape together, with Harry being the hero who saves Cedric.
In a 'Harry Potter Saves Bellatrix' fanfiction, perhaps Bellatrix is in a situation where she's about to be killed by other Death Eaters who think she's a liability. Harry, having a sense of justice and seeing the potential for redemption in her, steps in to save her. He could then try to show her the error of her ways, using his own experiences of losing loved ones to Voldemort's ideology. Bellatrix might initially resist, but gradually come to understand Harry's point of view.
Well, perhaps the vampire is being hunted by some dark wizards. Harry Potter, being the hero he is, uses his magic skills like the Patronus charm to fend off the attackers and save the vampire. Maybe the vampire has some crucial information about Voldemort that Harry needs.
Well, perhaps Harry stumbles upon a unicorn in the Forbidden Forest that is trapped by some dark magic spell. He uses his magic skills, like a Patronus charm to fend off the dark forces around the unicorn and then heals it with some herbology knowledge.
Maybe Harry uses his magic skills like the Patronus charm to protect the Jedi from the Sith. His ability to apparate could also help Jedi in quick escapes.
One possible plot could be that the Queen is in danger from dark wizards who want to take over the Muggle government. Harry, using his skills from Hogwarts, discovers the plot and uses magic to protect the Queen. He might use spells like Protego Maxima around Buckingham Palace.
Well, perhaps Harry could use his magic to defend Wakanda from some dark force. Maybe Voldemort has an alliance with an enemy of Wakanda and Harry has to stop them. He could use spells like Protego Maxima to shield Wakanda's borders and use the Patronus charm to fend off the Dementors that the villains might send.