A potential plot could be that an ancient spell or curse has been placed on both the Potter and Aragorn bloodlines. Harry, while exploring his family history in the wizarding world, stumbles upon some old records that hint at a connection to Aragorn. As he delves deeper, he finds that his Aragorn - descended heritage gives him a special connection to nature and leadership skills similar to Aragorn's. He then uses these newfound traits to fight against a dark force that is threatening both the wizarding world and Middle - earth, all while trying to understand and accept his new identity as part of two very different but powerful lineages.
The plot could involve some sort of hidden family connection being discovered. Maybe there's a long - lost magical artifact that reveals the link between Harry and Aragorn's bloodlines. It could also involve Harry having some new powers or abilities that come from his Aragorn - related heritage.
Well, it's quite possible for there to be a fanfiction with that plot. To find it, start with the big fanfiction platforms. AO3 has a vast collection and a good search function. FanFiction.net also has a lot of works. Another option is to join relevant forums. For example, there are Harry Potter and Lord of the Rings crossover forums where fans discuss and share fanfictions. They might be able to point you in the right direction if such a fanfiction exists.
A possible plot could be that Aragorn stumbles upon Harry during one of his travels. Harry is alone and in need of a family. Aragorn, having a kind heart, adopts him. They then embark on various adventures together. Harry might share his knowledge of magic with Aragorn and his companions, while Aragorn teaches Harry about survival in the wild, leadership, and the history of Middle - earth. Their relationship could grow stronger as they face different challenges side by side.
Maybe Aragorn adopts Harry because he sees the potential in him to be a great leader. He takes Harry under his wing to groom him into a leader who can unite different groups, just as Aragorn united the races in Middle - earth. Aragorn would expose Harry to the politics and power dynamics of Middle - earth, and Harry could use his own experiences of dealing with the wizarding world's power struggles to adapt and contribute. Also, Aragorn's strong moral compass would influence Harry to make more ethical decisions in his life.
One possible plot could be that there is some sort of magic that crosses the boundaries between the two fictional worlds. Harry is somehow transported to Middle - earth as a baby and Aragorn discovers him. He decides to raise Harry as his own. Harry then grows up with unique abilities, a combination of his wizarding powers and the skills of a ranger. He could then be involved in battles against Sauron, using his magic in unexpected ways to help the Fellowship.
The plot might revolve around a conflict where Harry's descent from Oberon makes him a target. Voldemort could want to use his unique heritage for his own dark purposes. Harry then has to navigate this new threat while also learning about his fae heritage, which includes things like learning new spells or magic related to Oberon's lineage.
In this fanfiction, it could start with a prophecy that links the two. Aragorn, who is used to prophecies from his own world, takes it seriously. He travels to find Harry and bring him to Middle - earth for training. Along the way, they bond over their shared experiences of loss (Aragorn's father and Harry's parents). Once in Middle - earth, Harry has to learn the ways of the land while also trying to figure out how his magic can be used in this new environment. Their relationship would be one of mutual respect and growth as they both learn from each other.
One way could be through a time - travel plot. A character from the Potterverse travels back in time to the world of Kratos and somehow gets involved with him, leading to a new bloodline.
In a large number of fanfictions, Harry is indeed made to be descended from the founders. This concept allows for a great deal of creativity. It could mean that he has an innate understanding of the magic that the founders were known for. Maybe he has a natural affinity for the secrets of Hogwarts if he's related to Helga Hufflepuff, or perhaps he has a more political influence within the wizarding world if his ancestry is linked to Rowena Ravenclaw. Fanfiction writers use this idea to expand on the existing Harry Potter universe in unique and exciting ways.
One possibility could be that they meet on a battlefield. Talion, with his undead skills and combat experience, and Aragorn, with his leadership and ranger abilities, recognize each other's strength. They might team up to fight against a common enemy like a horde of orcs. Aragorn could be initially skeptical of Talion's nature but soon realize they share a common goal of protecting Middle - earth.
Well, it could be that Aragorn somehow time - travels or there's a magical mix - up that results in him being Harry's father. Maybe Harry would inherit some of Aragorn's leadership skills and courage in a more obvious way. He could use a sword like Aragorn's Andúril in battles against Voldemort.