A common theme is friendship. Since they are from different backgrounds, their journey to become friends is often explored. Another is redemption. Cinder might be a character with a troubled past, and Ruby can be the catalyst for her change.
The theme of acceptance is quite prevalent. Cinder may be an outcast in some stories, and Ruby is the one who accepts her for who she is. This acceptance then leads to a series of events that transform both of their lives. Additionally, the exploration of different cultures or groups (if relevant in the fanfic's universe) can be a theme as well, as they bring their own experiences and knowledge to the relationship.
One major theme is the power of unity. In many 'cinder x ruby fanfic', they join forces against a common enemy. This shows how their combined abilities and personalities can overcome difficulties. Also, self - discovery is a theme. As they interact, they learn more about themselves and their place in the world. For example, Ruby might learn about her own strength through Cinder, and Cinder might discover her capacity for good through Ruby.
One common theme is redemption. Cinder is often portrayed as a character who might find redemption through her interactions with Ruby. Another theme is the power of understanding, as they come from very different sides in the RWBY world.
One common theme is the exploration of their contrasting personalities. Cinder is often seen as more mysterious and brooding, while Ruby is more cheerful and impulsive. Fanfictions like to play with how these two different personalities interact and complement each other.
One common theme is redemption. Maybe Cinder, who is often seen as a villain, is on a path to redemption because of Ruby. Another theme could be the power of friendship or a strange connection that defies their opposing natures.
Redemption is also a popular theme. Since Cinder is a villain, many fanfics like to see if she can be redeemed, often with Ruby playing a key role in that process. For example, Ruby's kind nature might inspire Cinder to change.
Another theme is the exploration of the unknown. Vampires are often associated with mystery, and when combined with the already complex characters of Ruby and Cinder from RWBY, it creates a situation where the characters are forced to explore new aspects of their world and themselves. For example, Ruby might have to face her fears of the supernatural, while Cinder could be using the vampires for her own gain in a world she doesn't fully understand yet.
One common theme is the exploration of the relationship between good and evil. Ruby represents the good side, and Cinder is often seen as the antagonist. Their relationship in fanfictions might explore how they can influence each other's views on this dichotomy.
Good character development makes a Ruby x Cinder fanfic great. If the author can show how their relationship evolves over time, it's a plus. For example, Ruby starting to see Cinder's more complex side.
Power struggle is a common theme. Since Cinder is a powerful character, often the OC has to either match her power or find a way to overcome it. For example, in many fics, the OC has a special power that can counter Cinder's Grimm - like abilities.
Some Ruby x Penny fanfics explore the theme of sacrifice. Given their different natures (Ruby as a huntress - in - training and Penny as a synthetic being), there could be situations where one has to sacrifice for the other. This could be for the greater good of their world or simply to protect their friendship. Also, the theme of acceptance is common, as they accept each other's differences and learn to work together and support each other despite their distinct origins.
Love and its discovery is also a frequent theme. As they spend more time together, the fanfics often explore how they gradually realize their feelings for one another. It could be through small moments like sharing a meal or a big event like saving each other's lives, which then leads to a deeper emotional connection between Ruby and Weiss.