One idea could be Ruby discovers she is the Winter Maiden in a moment of great danger. As she tries to control her new powers, she has to face off against Salem's minions who are after the power of the Maiden. Ruby's friends, Weiss, Blake and Yang, are initially shocked but quickly support her in her new role.
There are some great Ruby and Winter fanfictions out there. One might find on fanfiction.net or Archive of Our Own. Some fanfictions focus on their potential friendship, like how Ruby could learn a lot from Winter's discipline. Others might explore a more sisterly bond, given Ruby's relationship with Weiss and Winter being Weiss's sister.
There are quite a few great ones. 'Winter's Apprentice' is really good. It focuses on Ruby learning some new skills from Winter and their relationship evolving from a teacher - student dynamic to a friendship. The story has some really well - written action scenes.
Ruby could start having strange dreams related to the Winter Maiden's power before she actually becomes it. These dreams could be a foreshadowing of her future role. Once she becomes the Winter Maiden, her silver eyes might interact with the Maiden's power in a unique way, perhaps enhancing it or giving it a new aspect.
One popular plotline is the mentorship angle. Winter, being more experienced, takes Ruby under her wing. It could be training - related, like teaching Ruby advanced combat techniques. Another is the 'unlikely allies' plot, where they are forced to work together due to some external threat to Vale or the whole Remnant. And of course, there's the 'finding common ground' plot, which focuses on their differences but also how they discover shared values and interests.
Well, in a time travel scenario, Ruby and Winter's relationship would change drastically. Ruby might find herself in a position where she has to rely on Winter's knowledge of the past, which could make Winter seem more authoritative in her eyes. Winter, seeing Ruby from a different time, might be more open to her ideas as she realizes that Ruby has a unique perspective from the future. Their relationship could also become more sisterly. Ruby could see Winter as an older sister figure she can confide in, and Winter could feel a sense of protectiveness towards Ruby. This could be especially true if they face threats together during the time travel adventure.
Love and romance can also be a theme, although not always in a traditional sense. It might be more about the deep emotional connections between them. Some fanfictions might explore a more complex relationship where their feelings for each other are a mix of friendship, admiration and something deeper. For instance, Ruby might look up to Winter as a role model and at the same time have a special bond with Weiss, and these relationships can be explored in different ways in fanfiction.
One plot idea could be Ruby and Winter teaming up for a special mission. Maybe they have to infiltrate an enemy stronghold. Ruby's speed and Crescent Rose could be combined with Winter's ice powers and combat skills for some epic fight scenes.
Themes like adapting to new situations are quite common. Ruby and Winter are suddenly thrust into different time periods, and they have to figure out how to fit in. Another theme is the discovery of hidden truths. Maybe they find out secrets about their families or the origins of certain powers. And of course, there's the theme of heroism. They often have to be heroes in the past, facing threats that are different from what they're used to in their own time.