Maybe a story where Harry Potter himself is revealed to be an Immortal. He would have to balance his fight against Voldemort with the rules of the Highlander's world. This could add a whole new layer of complexity to his journey. He might learn new combat skills from the Highlander lore and use them against Death Eaters.
A plot could involve a Highlander character stumbling into the wizarding world. They are amazed by the magic but also find that their immortality gives them an edge in some magical duels. However, they also have to deal with the prejudices of wizards who don't understand their condition. This could lead to a story of friendship and mutual understanding between the two different universes.
Well, perhaps there's a Highlander who stumbles into the wizarding world. He might be confused at first by all the magic but then realizes he can use his immortality and combat skills to his advantage. He could get involved in the fight against Voldemort, using his unique abilities. Or, there could be a magical tournament in the Harry Potter world that also includes Immortals from the Highlander world, and they compete using both magic and their Highlander powers.
One idea could be that Xander discovers he has the immortality of a Highlander. He then has to navigate his newfound ability while still dealing with the usual supernatural threats in his world. Maybe he teams up with a Highlander character to learn more about his new condition.
One idea could be a Highlander character finding a Stargate and being transported to different planets. They could use their immortality to survive in the various dangerous situations on alien worlds and perhaps encounter Goa'uld who are interested in their immortality.
A possible plot could involve an immortal villain from the Highlander world using the Stargate network to spread chaos across different planets. The SG1 team, with the help of some friendly Highlander characters, has to track him down and stop him before he causes too much destruction.
A great plot for a Potter Manor fanfiction could involve a mystery that surrounds the manor. For instance, strange noises at night lead Harry to uncover a long - forgotten chamber. It could also be about Harry restoring the manor to its former glory, perhaps with the help of Hermione's research on ancient magic used in the construction of such manors.
A traveler could be from a different magical realm entirely and come to the Harry Potter universe. They bring with them unique magical abilities that both fascinate and frighten the wizards in the Harry Potter world. This could lead to a series of adventures where they either share their knowledge or are hunted down by those who fear the new magic they possess.
One idea could be that Hecate, being the goddess of magic, takes Harry Potter under her wing secretly to teach him ancient and powerful magic that Dumbledore doesn't know. This could lead to Harry having new abilities to fight Voldemort.
A possible plot in Harry Potter Planeswalker fanfiction is that a Planeswalker accidentally brings a dangerous creature from another plane into the Hogwarts grounds. This causes chaos as the teachers and students have to figure out how to deal with it. It could also be that a Planeswalker has a special connection to the magic in the Harry Potter world, like being able to sense the presence of magic in a way that wizards can't. They could use this ability to discover hidden secrets about Hogwarts or the wizarding families. Maybe a Planeswalker is on a quest in the multiverse and the Harry Potter world is just one stop on their journey, and their actions in the wizarding world have consequences for their overall mission.
One interesting plot could be a time - travel story in the Harry Potter wonderland. For example, a character goes back in time to the Marauders' era and gets involved in their adventures, while also trying to prevent a future disaster in the wizarding world. Another idea is a story where a new, powerful magic is discovered in the wonderland, and Harry and his friends have to figure out how to control it before it falls into the wrong hands. A third plot could be about an alternate reality where Voldemort won the war, and the remaining good characters have to find a way to reverse the situation in the harry potter wonderland.
One plot idea could be that Bella discovers she has a hidden magical ability that only Harry can help her understand and control. Maybe it has something to do with an ancient magic that's connected to Harry's destiny.