In some fanfics, an order summons might be a magical charm that appears as a constellation in the sky, visible only to those who are part of the 'Order'. For instance, if the Order is reforming to fight a resurrected Voldemort - related threat, the summons could call wizards from all over the wizarding world to a hidden location like the Room of Requirement.
Many fanfics depict the order summons as a form of enchanted parchment. The sender writes the details of the summons on the parchment. Once it's complete, the parchment magically replicates and finds its way to each member of the order. The parchment might have a special seal or symbol that only the members recognize, ensuring secrecy and authenticity.
I'm not entirely sure if there is a specific 'Harry Potter summons the devil' fanfic. Fanfiction is a huge realm with all kinds of ideas. But in the official Harry Potter universe, magic is more about good - evil magic like summoning the devil is not in line with the main story. It could be a very niche and probably not very popular idea among the more traditional Harry Potter fans.
One possible plot idea could be that Louise summons Harry Potter to her world to help deal with a dark magic threat that her world is facing but doesn't have the expertise to handle. Another could be that she summons him to participate in a magical tournament in her realm, which has different rules and challenges compared to the Triwizard Tournament.
One example could be a fanfic where the Weasley twins play an even more elaborate prank on Umbridge. They might transform her office into a giant Quidditch pitch, complete with flying bludgers that chase her around. Another is a story where Neville accidentally makes a potion that causes everyone's hair to turn into the shape of their Patronus. It's hilarious as Hermione has a book-shaped hair and Ron has a hair that looks like a piece of bacon.
One interesting example could be a fanfic that turns the sorting hat into a meme - making it give really sassy and modern - day comments during the sorting ceremony. Another could be a fanfic where the Weasley twins create meme - worthy magical pranks that spread throughout Hogwarts like wildfire.
Well, perhaps in the 'harry potter in the order fanfic', a major character's magical ability is suddenly revealed to be much different than what was originally thought. Like Hermione, who was always known for her book smarts, might have a hidden and extremely powerful combat - based magic that gets uncovered during a crucial battle. This would completely change the dynamics of how she is perceived within the Order and how she can contribute to their cause.
It would be very different from the normal Harry Potter stories. It might involve dark magic and a deviation from the moral code of the wizarding world. Maybe Harry would be in a desperate situation and make a really bad choice to summon the devil.
Well, in such a fanfic, Harry might summon a servant with unique powers. Maybe the servant could help him in his battles against Voldemort. For example, the servant could have the ability to detect dark magic from afar, allowing Harry to be more prepared for attacks.
It could be a house - elf. House - elves are known for their loyalty and their ability to do various tasks. They could be very useful to Harry, like helping him keep his dormitory clean or even spying on the Death Eaters.
One example could be a crossover with 'The Lord of the Rings' where Harry Potter and Frodo have a comical encounter. Maybe Harry accidentally casts a spell that makes Frodo's ring float away and they both scramble to get it back in a very clumsy and funny way.