One common theme is family. Since Raven is Ruby's mother, a lot of fanfictions explore their relationship in that context. It could be about Ruby trying to understand her mother better or Raven coming to terms with being a mother.
Another theme is the idea of redemption. Raven has made some questionable choices, and in fanfiction, Ruby can often be the catalyst for Raven to seek redemption. It's about the power of one character's goodness to inspire change in another.
One common theme is adventure. Writers often put Ruby and Raven in exciting adventures together, facing challenges and foes. Another is friendship exploration, delving into how their relationship develops and deepens over time.
One common theme is leadership. Ruby is a team leader in RWBY, and many fanfictions explore how she grows into that role, like dealing with difficult decisions and inspiring her teammates. For example, in some fanfictions, she has to lead her team through a very dangerous mission where every decision matters.
One common theme could be the exploration of Ruby's character growth in the face of abuse. Maybe she overcomes it and becomes stronger. Another theme might be how her friends react to her situation, whether they support her fully or struggle to understand what she's been through.
One common theme is Ruby's struggle with her new, darker powers as the Reaper. Writers often explore how she copes with the changes and the potential isolation it might bring. For example, she might have to hide her new form from her friends at first.
Character development is also frequently seen. Writers might explore how Ruby and Blake change over time, perhaps in response to the events in the RWBY universe. For example, how Blake deals with her past and how Ruby matures as a leader. Additionally, adventure themes are common, where they go on quests together, facing new enemies and exploring new places.
A common theme is power exploration. Since Raven is a powerful character, fanfictions often explore how her being Futa might enhance or change her powers. Another theme is identity. Raven's identity, both as a Futa and as a character in the RWBY world, is often questioned and developed in these stories.
One common theme is family. Since Raven left Yang, a lot of fanfictions use their relationship as a driving force for Raven's redemption. Another theme is guilt. Raven often has to confront the guilt of her past actions, like abandoning her team and daughter. And self - discovery is also a theme, as she figures out who she really wants to be in the face of her past mistakes.
Another theme could be acceptance. How her friends and the people around her accept and support her. It might show the growth of relationships within the RWBY universe as they learn more about Ruby's autism. There could also be themes related to Ruby's special interests within the RWBY world, like her weapon or her combat skills, and how her autism influences those interests.
The exploration of their backstories together is also a theme. Writers may create scenarios where Ruby and Cinder's pasts are somehow intertwined, perhaps revealing secrets that change their relationship in the RWBY universe.