Maybe they get transported to an alternate dimension where they have to rely on each other to find a way back. In this strange place, they discover new abilities within themselves and in the process, their relationship deepens. For example, Silver could use his psychokinetic powers in ways he never thought of before with Shadow's guidance.
Another plot could be that there is a mystery involving a powerful artifact. Silver and Shadow both have different reasons for wanting to find it. As they search for it, they encounter various obstacles and foes. Along the way, they learn about each other's pasts and motives, which changes their perception of one another.
One idea could be that Silver and Shadow are forced to team up to stop a new, powerful enemy that threatens their world. They start off distrusting each other but as they face challenges together, they begin to understand and respect one another.
One idea could be that they have to team up to stop a new powerful villain who is causing chaos across different zones. This villain could be creating some sort of energy disruptions that only their combined powers can counter.
A possible plot could be that both Silver and Tikal are called by a powerful, mysterious force. They find each other on this journey. Tikal's connection to the Chaos Emeralds and Silver's psychic powers interact in unexpected ways. As they face various challenges together, they grow closer. Silver is initially a bit of a loner, but Tikal's warm nature melts his heart, and they end up falling in love.
One idea could be exploring the backstory of the character in the Silver Trailer. Maybe show how they got their unique weapon and the training they went through. Another could be creating a prequel that leads up to the events in the trailer, like their first encounter with the Grimm.
Another plot idea could be a character who is mysteriously connected to the Silver Flame. They could have powers that are enhanced by it and have to hide this fact from others for some reason, like fear of being experimented on. For example, a new student at Beacon Academy discovers this connection and has to navigate through the challenges while keeping it a secret.
One idea could be exploring a different backstory for Alina. Maybe she was born with her powers but had to hide them in a more complex way than in the original story. Another could be a fanfic where Mal and Alina's relationship develops in a parallel universe where the Darkling never existed. This would change the dynamic of their love and how they face the challenges in Ravka.
One idea could be Silver coming from the future to prevent a new threat in the Sonic X universe that the others are unaware of. He might team up with Sonic and his friends in unexpected ways, like using his psychic powers to help them access hidden areas. For example, he could use his powers to levitate Sonic over a large chasm that the others can't cross.
Perhaps the reader is a gamer who somehow gets sucked into the game world where Lost Silver exists. They have to navigate the strange and often dangerous game environment while also getting closer to Lost Silver. Or, the reader could be a psychic who senses Lost Silver's presence and tries to help him move on from his tragic past, leading to a deep and emotional connection between them.
Some fanfictions might explore a more emotional side of their relationship. Maybe Silver is having trouble controlling his powers and Shadow, who has his own inner demons, helps him. They could have heart - to - heart conversations about their pasts, their loneliness, and how they can move forward. This kind of story can really dig deep into their characters and show a different aspect of their relationship.
Well, a plot could revolve around Shadow protecting Chris from a group of villains who are after Chris for some special ability he has. It could show how their relationship grows from a protector - protectee one to a true friendship. And then they might face a final big battle together against the main villain.
One idea could be that as a girl, Shadow has to face different challenges in a male - dominated Sonic world. Maybe she has to prove herself constantly to be accepted as a strong fighter.