One possible fanfiction could be about Ruby's journey as the Fall Maiden. She might struggle with the new power and the responsibilities that come with it. For example, she could face challenges from those who want to steal the Maiden's power for their own evil purposes. Ruby would have to learn to control the power quickly while still being true to herself and her values.
Cinder Fall herself could be a great antagonist. Since she has a history with the Fall Maiden power, she might want to reclaim it or prevent someone else from fully harnessing it. Her manipulative and power - hungry nature would make her a formidable foe.
One idea could be exploring the backstory of the Fall Maiden before she passed on the power. Maybe she had a secret love interest that was a threat to the order of Maidens. Another could be a story where the new Fall Maiden struggles to control her powers and has to learn from an unexpected mentor, like a character from the criminal underworld who has unique knowledge about the nature of magic.
A great plot could be that Ruby, as the Fall Maiden, discovers that the power she has is connected to an ancient prophecy. According to the prophecy, she is the only one who can stop an upcoming apocalypse. But to do so, she needs to find and unlock the true potential of the Fall Maiden's power. Along this journey, she teams up with some unexpected characters, learns about the history of the Maidens, and battles powerful foes who are trying to stop her from fulfilling the prophecy.
Well, one possibility is that Ruby has to face many challenges to become the Fall Maiden. Maybe she has to fight against other powerful foes who also want the power. She might struggle with the new responsibilities and powers that come with being the Fall Maiden.
Yes, in some RWBY fanfictions, Ruby can be depicted as the Summer Maiden. Fanfiction allows for creative interpretations and alternate storylines, so it's not uncommon to see such a concept explored.
A possible plot could involve Pyrrha having to face off against other powerful characters who want to steal her Maiden powers. She would have to use her combat skills, which she's already known for, in combination with her new Maiden abilities. Maybe she teams up with some unexpected allies, like a group of outcast Huntsmen who have their own reasons for wanting to protect the Maiden powers.
Emerald might be a character in this fanfiction. She could start as an enemy, trying to steal the Fall Maiden power from Ruby for Cinder. But as the story progresses, she might see the good in Ruby and switch sides. Neptune could also be there, providing some comic relief in the midst of all the serious Maiden - related business. And Glynda could be involved in training Ruby to control her new powers.
I'm not sure specifically as I haven't read this particular fanfiction. But generally, in RWBY, Ruby is a key character. A fanfiction with this title might focus on Ruby's journey towards becoming a maiden, exploring her growth, new powers she might gain, and the challenges she'd face along the way.
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.