In some fanfictions, Harry's Patronus could change because of a magical artifact. Maybe he discovers an ancient amulet that has the power to influence magic within him. As he gets closer to the amulet and starts to understand its power, his Patronus begins to change, say from a stag to a griffin, which could represent the new power and knowledge he has gained from the amulet.
A plot could revolve around a hidden prophecy that links the Basilisk and the Patronus. A young witch or wizard discovers this prophecy and realizes that they are the key to either saving or destroying the wizarding world. They must then navigate the dangerous relationship between the two magical entities. This could involve traveling back in time to learn about the origins of the Basilisk and the true nature of the Patronus magic, which could be much deeper and more complex than what was taught at Hogwarts.
One interesting idea could be exploring the complex relationships Harry has to re - evaluate. For example, his friendships might be strained as he changes sides. Another aspect could be how his view of the magical world's power structures alters. He might start to see the other side's motives in a different light, which could lead to some unexpected alliances.
One interesting Harry Patronus fanfiction could be where Harry discovers a new form of Patronus magic that has been long forgotten. This could lead to him having to face new dark forces with this enhanced power.
Some authors might make it a slow and gradual process. They'll show Harry noticing small differences in his Patronus over time. For instance, its color might start to fade or change slightly at first, and then as the story progresses, the form itself starts to transform. This gives a sense of mystery and builds suspense in the story.
One interesting 'Harry Potter Patronus Fanfiction' story could be about a character who discovers their Patronus has an unexpected form, like a phoenix when they expected a more common animal. It adds a new layer of mystery and self - discovery to the story.
Some fanfictions might explore how their Patronuses are linked to their family legacies. Since Harry has the connection to his father through the stag Patronus, and Ginny is part of the Weasley family, her Patronus could be related to some Weasley family trait. For instance, if the Weasleys are known for their loyalty and the Patronus of a dog represents loyalty, Ginny's could be a dog. And in the fanfiction, this could lead to interesting storylines where their Patronuses are not just symbols of their individual selves but also of their family heritages and how those heritages blend in their relationship.
Another plot could involve Harry being influenced by a family connection he discovers to a Death Eater. This newfound relation makes him reevaluate his beliefs and he starts to see the Death Eaters as more than just pure evil. He might think that by joining them, he can reform them from the inside.
In some fanfictions, the Basilisk could be reimagined in a different light. Maybe it's not just a mindless monster but has some sort of deeper purpose or connection to the Patronus magic. For instance, a fanfic could show that the Basilisk was once used in an ancient spell that now affects how modern - day Patronuses work. This would add a whole new layer of mystery and intrigue to the Harry Potter universe.
One possible fanfiction could be where Harry has to conjure his Patronus in the courtroom to prove his innocence. Maybe he's wrongly accused of using dark magic, and the Patronus is the only way to show his pure intentions.
In a fanfiction, Snape's Patronus could be the key to saving Lily from a dark magic curse in an alternate universe. Since the Patronus represents love and protection, Snape's doe Patronus might be able to break the curse that has trapped Lily's soul. As he sends his Patronus towards her, it glows with a powerful light that gradually dispels the dark magic surrounding her.