A plot could involve a magical artifact that has the power to connect different fictional universes. This artifact is discovered by both the Harry Potter world and Boromir's world. Boromir is sent to the Harry Potter world to retrieve it. Along the way, he meets Harry and his friends. They initially don't trust each other, but as they face challenges together, like dark wizards trying to steal the artifact for their own evil purposes, they learn to work together. Boromir's physical strength and Harry's magical abilities complement each other.
One possible plot could be that Boromir somehow gets transported to the wizarding world of Harry Potter. He could be mistaken for a Muggle at first, but his warrior skills and strong sense of honor quickly earn him respect. Maybe he joins the Order of the Phoenix and uses his combat experience to fight against the Death Eaters. He might also form an unlikely friendship with Harry, learning about magic and teaching Harry about his own world's combat strategies in return.
Voldemort could easily be the main antagonist. His goal of taking over the wizarding world and his use of dark magic would put him in direct conflict with Boromir and Harry. Boromir's sense of justice would not allow Voldemort's tyranny to stand, and Harry has his own vendetta against the Dark Lord.
One possible plot could be that Harry Potter discovers a magical portal that leads him to the underwater world of Aquaman. There, he has to learn the ways of the underwater society while also using his magic to help Aquaman fight against an evil force that threatens both the wizarding world and the underwater realm. Maybe a dark wizard has teamed up with a sea - based villain, and Harry's unique skills are needed to defeat them.
A plot might involve Harry Potter being sent to the underworld on a quest. Hades mistakes him for a threat at first. But as Harry shows his courage and resourcefulness, Hades starts to respect him. They could end up working together to stop a dark force that is threatening both the wizarding world and the underworld. Harry could teach Hades some magic spells, and Hades could show Harry the hidden powers of the underworld.
One possible plot could be that Alduin somehow enters the Harry Potter universe. Maybe he is summoned by a dark wizard who wants to use his power to take over Hogwarts. Harry and his friends then have to figure out how to send Alduin back to his own realm while also dealing with the chaos the dragon has brought to the school.
Sure, there are. The great thing about fanfiction is that it allows for all kinds of wild combinations. In 'Harry Potter Boromir' fanfiction, perhaps Boromir becomes a part of the Hogwarts faculty. He could teach combat skills or something related to his own experiences in Middle - earth. You can often find these by searching for specific tags on fanfiction platforms.
One common theme is the clash of different cultures. Since Boromir is from Middle - earth and the 'Harry Potter' series has its own unique magical world, there's often exploration of how their different values and ways of life interact. Another theme could be the idea of heroism. Both Boromir and the characters in 'Harry Potter' are often seen as heroes in their own right, and fanfictions might compare or combine their heroic journeys.
One possible plot could be that Voldemort uses the dark magic to create a plague similar to the one in The Walking Dead. The wizards and witches have to not only fight against the undead but also Voldemort's forces. Harry and his friends would need to find a way to stop the spread of the plague and defeat Voldemort once and for all, while also learning how to survive in a world filled with the walking dead.
One possible plot could be that some of the Hogwarts students accidentally end up in Hell (the setting of Hazbin Hotel). They could encounter the characters from Hazbin Hotel and have to find a way to get back. Maybe they initially think it's a part of some new magical realm or a powerful dark wizard's creation. For example, Harry Potter, Hermione, and Ron could meet Charlie and learn about her plan to rehabilitate sinners. The Hogwarts students might be skeptical at first but then start to see some similarities between the way magic is used in Hell and at Hogwarts.
Perhaps an Imperial Arm somehow gets transported into Hogwarts. The students, including Harry, start to notice strange things happening. Harry, being the curious and brave one, decides to investigate. He finds that the Imperial Arm has powers that can either help or harm the wizarding community, and he has to make a choice on what to do with it. As he delves deeper, he might learn about a connection between the wizarding world and the origin of the Imperial Arm.
One possible plot could be that Voldemort teams up with Loki. The Avengers and the Hogwarts crew would then have to work together. Harry, with his knowledge of magic, could teach the Avengers some basic spells to counter the dark magic Voldemort and Loki are using. Iron Man could use his technology to enhance some of the Hogwarts defenses. And Thor could share his knowledge of Asgardian magic with the wizards at Hogwarts.