In the fanfiction, Fenrir could be a part of an ancient prophecy that involves both the Harry Potter world and Loki's domain. Harry Potter, as the chosen one in his world, is destined to face Fenrir. But Loki has his own plans regarding the prophecy. He tries to manipulate the situation so that he can control the outcome. This would create a complex web of power struggles and alliances.
One idea could be a crossover where Fenrir from the Harry Potter universe somehow gets transported to the realm of Loki. Loki, being the trickster, might see Fenrir as a tool for his own schemes. Harry Potter, perhaps in a quest to stop some dark magic related to Fenrir, ends up following him and has to deal with Loki's antics as well.
The worlds might blend through the use of shared magical elements. For instance, both have magical creatures. The gargoyles' ability to turn to stone during the day and come alive at night could be related to some form of Transfiguration magic in the Harry Potter world.
One way to blend these worlds in a fanfiction is to have a time - travel or dimension - hopping plot. Suppose Bucky Barnes, while on a mission in the Marvel universe, gets caught in a strange energy wave that transports him to the Harry Potter world. There, he meets Harry Potter. Meanwhile, Steve Rogers follows to find Bucky. They find out that there are similarities between the two worlds in terms of good vs. evil battles. They then work together with Harry and his friends to fight against the dark forces in the Harry Potter world, and in the process, they bring some of their own ideas and values from the Marvel universe, like the importance of freedom and justice.
Well, often it's through magical elements. For example, a fanfic might have Harry Potter using his Patronus to save King Arthur from a dark spell. The Patronus, which is a big part of Harry Potter's magic, is introduced into the King Arthur setting.
The blend often occurs at a character level too. Characters from both series might form alliances or rivalries. A friendship between Legolas and Hermione could develop, with each sharing their knowledge of their respective worlds. Or perhaps Snape and Saruman could be pitted against each other, their cunning and knowledge of dark magic making for a great showdown. These character interactions help to bring the two very different worlds of 'Lotr' and 'Harry Potter' together in the fanfiction.
It can blend the two worlds by having the droids use their technological features in the wizarding world. For example, a droid's built - in map system could be used to navigate the complex corridors of Hogwarts. The droids could also introduce new concepts like energy sources that wizards might be able to adapt for their magic.
Character relationships are key. If a Hogwarts student befriends Quiet, they can learn from each other. The student can introduce Quiet to the concept of magic, and Quiet can show the student how to be more self - reliant in combat situations. This exchange of values and skills can help merge the two very different worlds of Harry Potter and MGSV.
In this fanfiction, the blending might occur when a group of wizards decides to study Muggle technology to gain an edge in the fight against Voldemort. They stumble upon the concept of the atomic bomb. Harry Potter then gets involved as he tries to prevent the wizards from misusing this knowledge. The story could show how the different cultures and power systems of the wizarding and Muggle worlds collide and interact around the idea of the atomic bomb.
A good way is to establish a common ground. For instance, if both universes have a form of magic, find a way to make those magics interact. Maybe Arturia's magic can be seen as an ancient form that has been forgotten in the Harry Potter world. Another way is through character relationships. Harry could look up to Arturia as a mentor figure, learning from her noble and chivalrous ways.
It blends the two worlds by using the familiar characters from Harry Potter and putting them in the irreverent and often chaotic situations of Cards Against Humanity. The characters' personalities play a big role. Harry, for instance, might be a bit more reserved in the game compared to Ron's more carefree approach.