Love and romance are quite common themes. The story might revolve around how Nuada and the female human OC overcome the differences between their species to fall in love.
One way to discover 'nuada x female human oc fanfiction' is to look for dedicated fanfiction communities centered around the source material that Nuada is from. These communities often have a section for fan - created stories. Additionally, you can try using more specific search terms on search engines, like adding the name of the franchise or setting related to Nuada along with the 'female human oc' part to narrow down the results.
Survival is a very common theme. Since Predators are usually seen as dangerous hunters, the human OCs often have to fight for their lives. Another theme is the unexpected alliance. Sometimes, for various reasons, the human OC and the Predator end up working together.
When creating the OC human, it's important to think about their growth throughout the story. Start with them being naive about Celestia's world. As the story progresses, they should learn and change. For example, they might start out being afraid of magic but by the end, they master a certain type of magic. Their goals and desires should be clear. If they want to find a way back home to the human world at first but then start to fall in love with Celestia's world and want to stay and protect it, this shift in their goals can create an interesting and complex character arc.
A common theme is the cultural clash between the asari and human cultures. Since they are from different species, their ways of thinking, social norms, and values can be very different, and this often creates interesting conflicts and resolutions in the stories.
One common theme is probably the journey of Nuada's redemption. It could involve him facing his past wrongs. Another theme might be the relationship development between Nuada and the reader, like how they grow to trust each other.
For the human OC, give her a distinct personality. For example, if she's shy, show how she reacts differently to Kaname's charm and Zero's intensity. Kaname is complex. Highlight his noble vampire side as well as his more manipulative tendencies. Show how he interacts with the OC, perhaps being overly polite at first. Zero is brooding. Emphasize his internal struggle between his vampire side and his hunter duties. Let the OC see this struggle and react to it.
Well, I've heard that some fanfiction forums dedicated to the Mass Effect universe often feature oc asari x human fanfiction. You could try joining those forums and asking the members for their favorite stories in this category. They might be able to point you to some hidden gems that haven't gained wide popularity yet.
Create a compelling plot. It could involve a mystery that Connor and the OC have to solve together, perhaps something related to the android revolution in the game's world. Don't just focus on the romance. Incorporate elements of the game's themes such as what it means to be human, the rights of androids, etc. This will make the fanfiction more engaging and true to the source material.
First, understand the characters well. Kara is kind - hearted and protective, so your OC should interact with her in a way that makes sense for her personality. For example, if your OC is more brash, there could be some initial conflict that then develops into a deeper connection.