There are fanfictions that explore Gilgamesh's past in a crossover context. Imagine a story where we see how he became the king he is in a world that has elements from different Fate installments. This could involve his early encounters with magic, his rise to power, and how his views were shaped. In addition, some storylines focus on Gilgamesh being a mentor figure in a crossover, passing on his knowledge of magic and combat to a new generation of Fate characters, which is an interesting twist on his character.
Well, a great storyline might involve Shirou and Saber swapping roles in some way. For example, Saber having to take on Shirou's daily life tasks, like going to school or doing mundane jobs, while Shirou has to lead in battles like Saber usually does. This role - reversal can bring out a lot of comical and also deep character - development moments. Also, a plot where they are in a parallel universe where their fates were different from the original story and they have to come to terms with these new versions of themselves.
One of the most interesting storylines could be Riku crossing over into another Disney - inspired world where he has to team up with unexpected characters. For example, he might end up in the world of 'Alice in Wonderland' and have to navigate the strange rules and characters there while still maintaining his connection to the Kingdom Hearts universe. It would be a really cool blend of the familiar Kingdom Hearts elements with the wacky world of Wonderland.
Another possibility is that Hermione, as a sorceress, has to face challenges within the Hogwarts community. For example, some students might be jealous of her powers and try to undermine her. But she overcomes this with her intelligence and the strength of her magic. In this type of fanfiction, we could see her form new alliances and learn new ways to use her magic to defend herself and those she cares about.
One interesting storyline could be Belle trying to break Rumpelstiltskin's curse in a different way. Maybe she uses her intelligence to find a loophole in the magic. Another could be a story where they meet in a different realm and form an alliance before their usual story events.
One interesting storyline could be a hybrid character struggling to find their place in the wizarding world. They might be shunned by both vampires and werewolves, yet possess unique powers that could be useful in the fight against dark magic. For example, their vampire side could give them enhanced speed and strength, while their werewolf side might offer a connection to nature that helps in certain spells or potions. Another could be a love triangle between a vampire - werewolf hybrid, a pure - blood wizard, and a Muggle - born witch, exploring themes of prejudice and acceptance in the magical community.
A great storyline might involve a fusion of the two worlds' mechanics. For example, the Velvet Room from Persona could have some connection to Joker's world. The Igor-like figure could offer Joker and his friends some new kind of power or knowledge that they use to combat a common foe. Or perhaps the Persona characters learn about Joker's Metaverse Navigator and try to replicate it in their world, which leads to all sorts of unforeseen consequences and adventures.
One of the most interesting storylines could be them teaming up on a secret mission in the wizarding world. Maybe they have to infiltrate a Death Eater stronghold together. Dorcas, with her skills, and Sirius, with his charm and bravado, would make a great duo in such a situation.
One interesting storyline could be their relationship dynamic. Runaan is often portrayed as a strong and stoic character, while Ethari is more of an artist and a bit more emotional. Fanfictions might explore how they handle their differences, like in a situation where Runaan's duties as an assassin clash with Ethari's more peaceful nature. Another aspect could be how they support each other during tough times in Xadia. For example, when Runaan is sent on dangerous missions, Ethari might be at home worrying but also finding ways to contribute to the cause from afar. There could also be fanfictions that focus on their backstory, like how they first met and fell in love, which could add a lot of depth to their characters.
One of the most interesting storylines could be Percy's adventures as the God of Rivers. He might have to deal with river spirits and their conflicts. For example, he could be involved in a power struggle between different river domains.
One of the most interesting storylines could be how their relationship develops in a modern world filled with new threats. Alucard's loyalty to Integra might be tested in different ways, like when facing new vampire clans. Maybe in some fanfictions, they have to work together more closely than in the original series, leading to a deeper emotional bond.