Obviously, Loki would be one of the main characters. He could be joined by Thor, his brother. Thor might represent the 'light' in contrast to Loki's more complex nature. Maybe they have to work together to combat the encroaching darkness. Another character could be Odin, who might have some knowledge or power that is crucial in dealing with this situation.
Loki would be the central figure. There could also be a female character, perhaps a powerful sorceress. She could be on a quest to preserve the light and initially be at odds with Loki but later realizes they need to team up. And then there could be a dark entity, an ancient being that is the source of the 'darkness flooded in light' situation. Loki has to face this entity in the end.
Well, it could be about Loki finding himself in a situation where darkness is encroaching upon a world that was once filled with light. Maybe he has to face some dark force that is slowly consuming the realms he cares about. And he might be the only one who can stop it, perhaps using his trickery and magic in ways that no one expected.
Since it's a Twilight fanfiction, it might focus on the Cullens as the main characters. One of them could be the one to bring the 'light in the darkness'. For instance, Carlisle with his moral compass and leadership could be the central figure in a story about guiding the family through a difficult time in the Twilight - like world. Or perhaps it could be a new Cullen - like vampire introduced in the fanfiction who plays this role.
It's hard to say exactly who the main characters are without reading the fanfiction. But if we consider the themes of 'darkness in the light', it could be characters who are on the verge of losing their way in the light - filled Yu - Gi - Oh world. It might be some of the minor characters from the original series who are given more depth in this fanfiction. For example, a character who was always in the background but now is in the center of a story arc dealing with the discovery of a dark power within a seemingly innocent card. Or it could be an entirely new character created by the fanfiction author who has a unique connection to both the light and the darkness in the Yu - Gi - Oh universe, and through their journey, we explore the concept of 'darkness in the light' more deeply.
I'm not sure specifically as we don't have more details about the story. But it could be an ordinary person who becomes a hero, like a young girl who finds a cure for a deadly disease in a world full of suffering. She would be one of the main characters.
I don't have enough information to say who the main characters are as I don't know the particular 'a light in the darkness story'.
In this fanfiction, aside from the core RWBY team, there could also be other important characters. Ozpin might play a role as he often has knowledge and guidance to offer. Qrow Branwen could also be involved as he is Ruby's uncle and has his own set of skills and connections. Additionally, characters like Pyrrha Nikos might make an appearance if the story is set in a timeline where she still exists, and she could be a powerful ally in the battle against the darkness.
I'm not sure specifically as it depends on the author's creation. But it could be characters who are on a journey to understand the true nature of darkness and light, like a young adventurer or a wise old sage.
One main character could be a young scientist. This person could be intrigued by Loki's arrival and his other - worldly powers. They might try to study him in a non - invasive way, which could lead to some interesting interactions between them. Another character could be a street - smart kid who Loki befriends. The kid shows Loki the ropes of the city and in return, Loki protects the kid from the local bullies.
There could be a mysterious old man who lives in a secluded forest. He has a special bond with a Pokemon that is both light and dark in nature. He gives cryptic advice to young trainers who pass by his forest, guiding them on their journey to understand the balance between light and darkness. And then there's a young girl who can communicate with Pokemon through dreams, especially those related to light and darkness.
The main characters would surely include Loki, who might be the catalyst for the story. Then there's Thor, his brother, who would try to bring Loki into the Christmas spirit. Hulk could also be a main character in a funny way. Imagine Hulk trying to put up Christmas lights and accidentally destroying half of the building. And of course, the core Avengers like Hawkeye, who could be teaching Loki how to shoot arrows at Christmas - themed targets, and Vision, who might explain the deeper meaning of Christmas to Loki using his knowledge of the Mind Stone.