Perhaps a vampire has a connection to Harry Potter's past that Tonks uncovers. For example, the vampire could have known Harry's parents and has some important information that could help Harry in his fight against Voldemort. The story could then revolve around Tonks protecting the vampire from those who want to silence him while also trying to get the information to Harry.
One idea could be that Tonks discovers a hidden vampire community in the wizarding world while on a mission related to Harry Potter. Maybe the vampires are being wrongly accused of attacking wizards, and Tonks, with Harry's help, tries to uncover the truth.
A possible plot could be that Harry Potter discovers a prophecy that involves Fleur and a powerful vampire. The prophecy states that only together can they defeat a new dark force rising. Along the way, Fleur has to struggle with her own identity as she is part Veela and now has vampire traits after an encounter, and Harry has to deal with the mistrust of the wizarding community towards Fleur's new state.
One plot idea could be Tonks helping Harry to master some of the more difficult Patronus spells. Since Tonks is a skilled witch, she could offer unique insights and training methods. Another idea is that they go on a secret mission together to find out more about Voldemort's hidden lairs. They might have to use Tonks' Metamorphmagus abilities to their advantage.
One idea could be that Tonks gets involved in Harry's search for Horcruxes. Maybe her Metamorphmagus abilities help them in disguising and sneaking into places undetected. For example, she could transform into a Death Eater to infiltrate their meetings and gather information.
One plot idea could be that Tonks uses her Metamorphmagus abilities to help Harry in his undercover missions during the war. For example, she could change her appearance to infiltrate Death Eater strongholds with Harry. Another idea is that Harry discovers a new side of Tonks' personality that he didn't expect, and they bond over their shared experiences of loss. Maybe they both lost someone important to them in the fight against Voldemort and find comfort in each other.
One plot idea could be a crossover where the magical world of Harry Potter collides with the vampire world of Twilight. Maybe Tonks and Alice Cullen team up to solve a mystery that involves both magic and vampire powers. And Tanya could be involved as a sort of rival or an ally depending on the story.
Another plot could involve them being chosen for a special mission by Dumbledore. Because they are the same age and have shown particular skills, Dumbledore thinks they can work well together. They have to travel to a far - off wizarding community to retrieve a powerful magical artifact. Along the way, they face many challenges and their relationship grows stronger.
Well, one idea is that Tonks uses her Metamorphmagus powers to create elaborate pranks around Hogwarts. She could change into different teachers or even inanimate objects to startle students and have some light - hearted fun. It would be a humorous take on her abilities.
A possible plot is that Harry and Tonks time travel to a point where the creation of Horcruxes was just beginning. They could try to stop Voldemort from splitting his soul, which would change the whole course of the wizarding world's history. They would face many challenges, like not being discovered by Voldemort or his followers. Also, Tonks might use her skills to distract or mislead some of the Death Eaters while Harry looks for a way to destroy the Horcrux - making materials or the places where Voldemort hid them.
One idea could be the cultural and family clashes that come with such a contract. Maybe Harry's friends are shocked and have mixed reactions. Another could be how Harry and Tonks grow to understand and care for each other in the context of this contract. For example, they start off as strangers in this arranged - like situation but gradually find common interests.
In a fanfiction, Tonks could be the one to introduce Harry to some of the more underground and less - known magical communities. This could lead to all sorts of adventures as they meet unique wizards and witches. Another plot could involve Tonks teaching Harry how to better understand and communicate with magical creatures, which could be useful in his future battles. Additionally, a story where Tonks and Harry are on a mission to protect a young, powerful, and endangered magical being from dark forces would be a great non - adult fanfiction idea.