Well, you could start with the idea that the Duel Monsters exist in a hidden part of the wizarding world. Wizards have been using them secretly for centuries, but it's not common knowledge. Then, a young wizard stumbles upon this secret and starts to explore it, integrating Duel Monsters into his regular duels at Hogwarts.
You can blend them by having the characters' personalities influence how they play Duel Monsters. In Harry Potter, we have different personalities like Hermione's studious nature, Ron's loyalty but also his occasional jealousy, and Harry's bravery. In a fanfiction, Hermione might study all the Duel Monsters rules and strategies intensively, Ron might be really attached to a particular Duel Monsters card because it reminds him of something from his wizarding life, and Harry might use Duel Monsters as a way to face his fears and become even braver. This way, the essence of the Harry Potter characters is carried over into the Duel Monsters world within the fanfiction.
I know there are some fanfictions in this vein. When looking for them, it's important to keep in mind that different authors will have different takes on how Harry Potter would interact with Duel Monsters. Some might have him be a natural at the game, using his magical skills from Hogwarts to his advantage. Others could make it a struggle for him to adapt to this new type of magic. Reading reviews from other readers can also be helpful in finding the better-written ones.
One way to blend them creatively is through character crossovers. Imagine a character from 'Brave New World' like John the Savage finding himself in the wizarding world of 'Harry Potter'. His different upbringing and values would create interesting conflicts. For example, he might be shocked by the use of magic as it goes against the highly controlled and technological society he comes from. He could question the hierarchical system in Hogwarts which, although different from his own world, still has a sense of order that he might not fully understand or accept.
Well, a prevalent theme is adaptation. Harry has to adapt to the new rules and mechanics of Duel Monsters. This often involves a learning curve which can be an interesting part of the story. Also, discovery is a big theme. Discovering new monsters, new strategies, and how it all fits into his understanding of magic. Additionally, there's the theme of power. How the power of Duel Monsters compares to the power he has in his own wizarding world and how he can use it to his advantage or face challenges because of it. There are many more possible themes depending on the creativity of the author.
One way is through character creation. For example, a new character could be based on a Norse god or goddess, with their powers and personalities reflected in the Harry Potter world. So, like a character inspired by Thor could have the power of lightning in the magical context of Hogwarts.
The worlds can be blended by having Barbie visit Diagon Alley. She could be amazed by all the magical items and use her fashion sense to customize her wizarding robes. For instance, adding some sparkly elements that are typical of Barbie's style.
The blend can occur through the use of magic in relation to trigonometry in solving problems. For example, in a fanfiction, a magical creature is lost in a forest that is magically generated with trigonometric patterns. The characters need to use their knowledge of both magic and trigonometry to find the creature. Also, a character's magical power could be related to their understanding of trigonometry, so as they learn more math, their magic becomes stronger and more versatile.
Sure. Fanfiction gives authors the freedom to take the concept of dueling in the Harry Potter universe and expand on it. Harry Potter is a skilled wizard, and in fanfictions, he could be involved in duels that test his skills even further. Maybe he has to duel a powerful dark wizard that the original books didn't mention, or he could be in a magical tournament where dueling is the main event. There are countless possibilities.
Well, often in such fanfiction, the magic systems are combined. For example, spells from Harry Potter like 'Expelliarmus' might be used in the Skyrim setting. Writers might have a character who is a wizard from Hogwarts suddenly find themselves in Skyrim and use their magic there. It creates a really interesting crossover where the different rules and powers of each magic world collide.
In some fanfictions, the Industrial Revolution might be incorporated into the Harry Potter world by introducing new magical devices created with industrial - era concepts. For example, there could be magically - powered factories in the wizarding world producing potions or wands on a larger scale. This could change the economy and social structure within the wizarding community, as mass production might lead to different power dynamics among the wizarding families who own these new industries.
Perhaps there could be a tournament where the students have to combine their wizarding skills with Duel Monsters strategies. A character could be really good at using Fire - based spells and then pairs that with Fire - type Duel Monsters cards. They would need to learn how to balance the two forms of combat to win the tournament.