One common theme is redemption. Since Nagini is often seen as a dark creature in the original series, many fanfics explore her journey towards redemption with Harry's help. Another theme is the exploration of the relationship between humans and magical creatures. Harry represents the human side, and Nagini the magical creature, and their interactions can show different aspects of coexistence.
One interesting Nagini fanfic could be one that explores her backstory before she was fully under Voldemort's control. Maybe it delves into her time as a Maledictus, how she coped with her condition, and the choices she made that eventually led her to Voldemort. It could show a more sympathetic side of her.
Some fanfics might explore Nagini's connection to the other Horcruxes. Since she was the last Horcrux to be destroyed, perhaps there was some kind of communication or power exchange between her and the other Horcruxes that we didn't see in the books. This could add a whole new layer of mystery to the story.
It could start with hostility. Harry sees Nagini as a tool of Voldemort, and Nagini is loyal to Voldemort at first. But then, some unexpected events might force them to interact more. For example, they could be trapped together in a magical place, and they have to rely on each other to get out.
A fanfic could also focus on a scenario where Nagini has a change of heart. For example, she could start to resist Voldemort's control due to some unforeseen bond with a character in the Harry Potter universe, like a kind wizard who tries to communicate with her on a deeper level.
You can try fanfiction websites like Archive of Our Own (AO3). There are a large number of Harry Potter fanfics involving Nagini on it. Just use the search function and type in 'Harry Potter Nagini' to find relevant stories.
Yes, there are some out there. You can try searching on fanfiction - specific websites like Archive of Our Own. Just be aware that the concept is quite unusual as Nagini is a snake and in the original series, not really a typical love interest for Harry.
Well, in certain fanfiction scenarios, Nagini could be magically bound to protect Harry. Maybe a spell was cast that made her loyalty shift from Voldemort to Harry. So she would use her venomous attacks or her stealthy movements to keep Harry safe from Death Eaters or other dark forces. She might also be able to communicate with other snakes in the area and get them to help in protecting Harry.
In many Harry Potter and Nagini fanfictions, the relationship between them is often explored in unique ways. Some might depict Nagini as having a more complex personality than in the original books. For example, she could be shown as a victim of dark magic rather than just a tool of Voldemort.
One possible plot could be that Harry discovers a young Tom in a difficult situation, perhaps an orphanage similar to his own past. He decides to take Tom under his wing out of a sense of empathy. Harry then tries to guide Tom away from the dark path he originally took in the canon. For example, he might introduce Tom to the world of positive magic and friendship early on, which could change Tom's perspective on life and magic.