One popular theme is the power struggle. The Winter Maiden has a great amount of power, and many fanfictions explore how different characters either try to gain control of it or protect it from others. For example, in some stories, villains scheme to steal the Maiden's power.
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.
One great RWBY Winter Maiden fanfiction is 'Winter's Ascent'. It delves into the backstory of the Winter Maiden, exploring her training and the internal struggles she faces. The author does an excellent job of depicting the RWBY universe's lore within the fanfiction.
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.
One great fanfiction could be where Glynda and Winter Maiden team up to face a common threat in Remnant. It might involve their different powers and how they combine them effectively.
One popular theme is the combination of powers. Fans love to see how the Guyver's powerful abilities mesh with the unique semblances in RWBY. For example, a character with a speed - based semblance might use the Guyver's enhanced physical capabilities to become even faster. Another theme is the exploration of new threats. With the Guyver technology in the RWBY world, new and more dangerous enemies can be created, which makes for exciting storylines.
Self - discovery is also a big theme. Ruby has to figure out who she is now that she is a Maiden. This can involve exploring her limits, her fears, and her new place in the RWBY universe. Additionally, the theme of good vs. evil is prevalent, with Ruby using her Maiden powers to fight against the forces of darkness.
One common theme is self - discovery. The OC Maiden often has to figure out her powers and her role in the RWBY world. Another theme is friendship. Just like in the main RWBY series, the OC Maiden forms bonds with other characters. For example, she might team up with Ruby and her friends.
I think Ruby could be the most likely. She has always been at the forefront of the team, with her leadership skills and strong will. Her silver eyes already give her an edge, and as a Maiden, she could use her speed and new powers to protect her friends even better. Also, her innocent - looking exterior but strong - hearted interior would make for an interesting contrast with the powerful Maiden powers.
The popularity might come from the fact that the RWBY fandom loves to explore different relationships. Winter has a complex character, and pairing her with another female character allows for unique character dynamics to be explored.