There is often a theme of sacrifice as well. In many of these fanfictions, either Cinder or Amber may be put in a position where they have to sacrifice something for the other. It could be their power, their reputation, or even their life. This theme adds a layer of depth and emotional intensity to their relationship. Additionally, the exploration of their pasts and how it brought them to this point in their relationship is also a common theme.
You can try fanfiction websites like Archive of Our Own (AO3). There are a large number of RWBY - related fanfictions there, including ones about Cinder Fall and Amber. Another option is FanFiction.net, which also has a wide range of works. Just search for 'Cinder Fall x Amber' in the search bar on these sites and you should be able to find some interesting stories.
One common theme is power struggle. Cinder is often power - hungry, and Amber is a Maiden with great power. Their interactions can be centered around who is more powerful or who gets to control certain things. Another theme is redemption. Some fanfictions explore the idea of Cinder finding redemption through her relationship with Amber.
Perhaps the fanfiction could be about Cinder Fall being sent back in time to a point before she became evil and meeting Ruby as a child. Ruby's kindness towards Cinder at this early stage has a profound impact on her. As Cinder grows up, she constantly struggles between her original dark destiny and the new path that Ruby's friendship has opened up for her. This internal conflict could be the central theme of the story.
One common theme is power. Given their positions as antagonists in the original work, fanfiction often explores how they use or abuse power, both together and separately. Another theme is loyalty, as they are partners in crime, so stories might focus on how far they would go for each other.
There's a fanfiction called 'Cinder and Amber: A Forged Bond'. In this story, it begins with their initial encounter and gradually builds up their relationship. It shows how Cinder's ambition and Amber's protectiveness of the Relic play into their connection. The author does a great job of describing their emotions and the power dynamics between them.
At first, it could be full of tension. Cinder Fall is used to being a villain, and Ruby is a huntress-in -training. But as they interact more, they might start to understand each other. Ruby could see the pain behind Cinder's actions, and Cinder could be intrigued by Ruby's unwavering hope.
Love against all odds is also a big theme. Given Cinder's nature and the world she exists in, the relationship between her and the male reader is often portrayed as something that has to overcome many obstacles, whether it be social status differences or her own past actions.
In lemon fanfiction, Cinder Fall might often be portrayed as more seductive. Her usual confident and powerful traits in the original RWBY series can be enhanced and sometimes used in a more alluring way to drive the romantic or more adult - themed aspects of the story.
I'm not sure of specific titles off - hand, but often fanfiction about Cinder Fall and Roman will delve into their criminal partnership in more depth. Some stories might show how they met and started working together, perhaps with some backstory added to their characters that wasn't fully explored in the original source material. Another aspect could be how they interact during different heists or battles, with a focus on their unique dynamic.