Sure. In the world of fanfiction, the sky's the limit. Since 'Harry Potter' has such a rich tapestry of magic and mystery, it's not at all surprising that someone might write a story where Harry Potter has something to do with dragon serpents. It might be a story where he has to tame a dragon - serpent hybrid as part of a dangerous quest, or maybe he finds out he has some sort of ancestral link to them.
In some Harry Potter fanfictions, serpent familiars are often portrayed as mysterious and powerful. They can be shown as having a deep connection with their owners, almost like an extension of their magical selves. For example, they might be able to sense danger before their owners do and act as protectors.
A common trait is their intelligence. They are often much smarter than ordinary snakes. Another trait is loyalty to their owners. They will usually stay by their side through thick and thin.
One possible plotline could be that Harry discovers he has the ability to communicate with dragon serpents. This newfound skill helps him in his fight against Voldemort. Maybe the dragon serpents know of a hidden weakness of Voldemort's that no one else does.
There could also be original characters created specifically for the fanfiction. For instance, a young wizard or witch who has a natural affinity for serpents and is an outcast because of it. They meet Harry and together they explore the mysteries related to the serpent. This character could bring a fresh perspective to the story and have their own backstory and motives.
One interesting plotline could be a serpent that has a special bond with Harry. Maybe it's a magical serpent that can communicate with him and helps him in his adventures. For example, it could lead him to hidden secrets in Hogwarts that are related to the founders and their connection with serpents.
Obviously, Harry Potter himself could be a main character. He might be drawn into the story of the serpent king due to his inquisitive nature and his constant fight against dark forces. His friends like Hermione and Ron could also be involved, providing their unique skills and knowledge.
A great plotline might involve the serpent king being a misunderstood figure. Instead of being a pure villain, he has his own motives and goals, like protecting a certain part of the magical world that has been long forgotten or oppressed. In the fanfiction, Harry could find himself in a moral dilemma of whether to fight or side with the serpent king.
Often, Harry Potter is one of the main characters as it's a crossover. The fem serpent character is also a main character. She could be a new student at Hogwarts who is part - serpent, or she could be a mysterious figure from outside the school who enters Harry's world.
There's also 'A Fem Serpent's Adventure in Potter's World'. In this fic, the female serpent could be from a different magical realm and gets involved in the events at Hogwarts. It could show her trying to adapt to the new environment while also dealing with the mysteries and challenges there. For example, she might help Harry solve a difficult mystery using her serpent - like instincts.