He could bring some of his unique spells from Hogwarts. His Patronus charm could be a very useful tool in the often - dark and dangerous Dresden Files world. It could help him fight off some of the nastier creatures there. On the other hand, the wizards in the Dresden Files might view him with suspicion at first, not knowing exactly where his loyalties lie.
One interesting crossover could be the use of magic systems. In the Dresden Files, magic is more gritty and has a cost, while in Harry Potter it's more structured. A fanfiction might explore what happens when a wizard from Harry Potter's world tries to use Dresden Files magic, or vice versa.
One idea could be that Harry Potter accidentally travels to the world of the Dresden Files. He could meet Harry Dresden and they team up to fight a dark magic threat that is affecting both their worlds. Maybe a powerful dark wizard from the Potterverse has found a way to use the magic from the Dresden Files world to enhance their power.
His relationships would be different. He wouldn't have the same kind of friendships as he did at Hogwarts. Instead, he'd form more tenuous alliances based on mutual self - interest. His view of magic would expand greatly as he discovers the different types of magic users and creatures in the Dresden Files world. This new exposure would shape his character into someone more complex and adaptable.
Well, in the original Harry Potter, magic is often about waving a wand and saying a spell. But in the Dresden Files, it's more about willpower and knowledge of the supernatural. In fanfiction, they might blend these. For example, a character might use a Harry Potter spell but with the added requirement of Dresden Files - style willpower.
One interesting 'Harry Potter Dresden Files' fan fiction could be one that combines the magic systems of both. For example, a story where Harry Potter and his friends encounter a problem that can only be solved by using Dresden's more gritty and street - wise approach to magic. Maybe they have to deal with a dark wizard who is using a blend of muggle - influenced dark magic that is more in line with the Dresden Files universe.
Severus Snape and Murphy from the Dresden Files. Snape has his cold, brooding exterior and complex past, while Murphy is a tough, no - nonsense police detective dealing with the supernatural. Their interactions could be very tense, with Snape looking down on Murphy's 'mundane' ways of dealing with magic at first, but later realizing she has her own strengths.
First, you need to be really familiar with both universes. Read all the Harry Potter books and watch the movies, and also read the Dresden Files series. Then, think about a concept that would bring the two together in an interesting way. It could be a simple idea like a character exchange or a more complex one like a merged magic system. After that, start with an outline of your story, including the main characters, the plot, and the setting.
They expand the world. For example, they might introduce new magical concepts or creatures that we haven't seen in the main series. This enriches the overall lore.
Probably 'Storm Front'. It was one of the first to be released and has a large following. It sets up the world and characters really well for new readers.