I'm not sure specifically as I haven't read it in detail. But generally, it might be about a powerful sage or wizard. Maybe it involves his adventures, battles, and the development of his powers.
One popular Kara and Mon - El pregnant fanfiction might be 'A New Beginning'. It focuses on how they navigate their relationship while expecting a child. It shows Kara's struggle between her superhero duties and impending motherhood in a really interesting way.
You can try Archive of Our Own (AO3). It has a vast collection of fanfictions, and there are likely to be many about Kara and Mon - El being pregnant. Just use the search function and type in the relevant keywords.
One key feature could be its unique characters. They might have complex personalities and abilities that drive the story forward. Another aspect could be the world - building. It may present a vivid and detailed fictional world with its own rules and cultures. Also, the plot might be full of twists and turns, making it engaging for readers.
I'm not entirely sure as I haven't read every volume, but usually there is a central protagonist who is often the'saikyou kenja' (the strongest sage). There might also be supporting characters like friends or allies who help the main character in their journey.
Obviously, Supergirl herself should be included. Her presence can add more drama and conflict, especially if she has mixed feelings about Lena and Mon - El's relationship. J'onn J'onzz could also be a great addition as he can offer his wisdom and alien perspective.
Well, a possible plotline is where Lena starts to develop feelings for Mon - El while he is still trying to figure out his place in the world of Supergirl. There could also be a plot where they get into an argument over the best way to deal with a new alien threat, but later reconcile and come up with an even better plan together.