In a fanfiction, the combination could work like this. Lelouch's Geass, which is a power of the mind, could interact with the magic related to the mind in the Harry Potter world, such as Legilimency and Occlumency. Maybe Lelouch could use his Geass to break through the Occlumency defenses of a powerful wizard. On the other hand, the magic of Harry Potter, like the Patronus charm, could be used to protect against the negative effects of Geass. If someone was being influenced by Geass against their will, a Patronus could drive the Geass influence away.
The magic in Harry Potter is based on spells, potions, and magical creatures. In a fanfiction, Geass could be seen as a special type of spell or curse. For example, a Geass could be cast like a spell, but with different rules. Maybe it requires eye contact like in Code Geass, and the effects are more long - term and powerful than normal spells. The magic system in Harry Potter could also be used to counter or enhance Geass. For instance, a powerful anti - curse spell could be used to break a Geass if it's seen as a form of dark magic.
Magic spells from Harry Potter can be given Magic the Gathering - like mechanics. For example, the 'Expecto Patronum' spell could cost a certain amount of mana (like white mana for its purity aspect) and be used to protect against dark forces, which in the fanfiction could be related to certain types of Magic the Gathering creatures like demons.
The magic in 'Harry Potter' is mainly based on spells, potions, and magical artifacts. In 'Devils and Realist', there are different types of powers related to demons and the political power plays. In a fanfic, one could combine them by having a spell that can summon or control a demon from 'Devils and Realist'. For example, a powerful wizard in the 'Harry Potter' world discovers an ancient spell that links to the demon realm in 'Devils and Realist' and starts to experiment with it, but quickly realizes the danger as the demons have their own motives and power hierarchies.
One way could be to give Harry the Geass power. So, he could use it to control the actions of Death Eaters or Voldemort himself. He might start to make more strategic and calculated moves like Lelouch, using his new power to outwit his enemies. Another aspect could be in the political side. Maybe the wizarding world becomes more like Lelouch's world with different factions vying for power and Harry has to play a political game as well as fight against the dark forces.
Well, in Narnia, there's the magic of Aslan which is more of a divine and nature - based magic. In Harry Potter, it's more about spells and potions. You could have a situation where a wizard tries to learn the magic of Aslan. For example, Hermione might be intrigued by the magic that brings Narnia to life and tries to study it. She could combine her knowledge of wizardry with the Narnian magic to create new spells.
The magic in Harry Potter is mainly spell - based, while in The Dragon Prince it is more about primal sources. In fanfiction, a character could try to combine the two. For instance, a wizard could use a spell to enhance the power of a primal source connection. They might use the Wingardium Leviosa spell to levitate an object charged with primal magic.
You could create a new type of magic that combines the two. Let's say there is a character in the fanfiction who is half - wizard from Harry Potter and half - something related to Black Butler (maybe has a demon ancestor). This character has a unique magic that is a blend of spell - casting and the ability to make deals with supernatural forces. Their spells might have a different effect because of the demonic influence. For instance, a simple levitation spell could also cause a small amount of fear in those around them because of the dark undertones from the Black Butler magic.
The magic in Harry Potter is based on knowledge, intention, and wand - work. In a fight against Janemba, wizards could use the power of Transfiguration. They could transform the environment around Janemba into something that restricts his movement or power. For example, turning the ground into quicksand or the air into a thick, unbreathable substance. But Janemba's power might be able to break through these magical constructs easily. So, the wizards would also need to rely on their wits and the collective power of the wizarding community. They could gather ancient magical artifacts or seek the help of magical creatures like the centaurs, who have their own deep understanding of magic and might be able to offer some unique solutions.
First, understand the character of Lelouch thoroughly. Know his motives, his strengths, and his weaknesses. For example, his desire for justice and his complex relationship with his sister. Then, create an interesting plot. It could be an alternate timeline, like what if Lelouch didn't get his Geass power? Also, make sure to keep the writing style engaging. Use vivid descriptions of the Code Geass world, like the mechs and the political intrigue.
In a crossover, the magic of apparition could be a source of horror. A character could apparate to a wrong place that is filled with Creepypasta - inspired horrors. Maybe a place that looks like Hogwarts but is full of twisted versions of the people and things they know. The magic of divination could also be combined. Instead of normal prophecies, a seer could start seeing visions of Creepypasta - like events that are about to happen in Hogwarts. And the magic of the Room of Requirement could be used in a really dark way. Instead of providing what the user needs, it could trap a character in a never - ending nightmare - like scenario filled with Creepypasta elements.