One possible plotline could be Momonga exploring the human world in his new form. He might encounter various human emotions like love, friendship, and jealousy for the first time. Maybe he gets a job to blend in and has to deal with a difficult boss or annoying coworkers.
A third plotline might be Momonga trying to find a way back to his original form. In the process, he forms deep bonds with certain humans who help him on his quest. He could learn about the value of human connection and how it differs from his relationships in the Overlord world.
He might have a tall and imposing stature, with piercing eyes that still hold a hint of his otherworldly power. His hair could be a dark color, perhaps black or a deep shade of purple, and it would be neatly styled.
One common theme is his adjustment to the human world. Since he's from a different form originally, how he copes with human emotions, relationships, and society is often explored.
You can try fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. Just search for 'Momonga human form' on their search bars, and you'll likely find a variety of fanfictions related to it.
Perhaps there's a fanfiction where a group of gorillas escape from a zoo and find their way into the heart of the city. A kind - hearted human family takes them in and tries to keep them hidden. However, as time passes, the gorillas start to show unique abilities that attract the attention of both good and bad elements in the city. This leads to a series of adventures as the family and gorillas try to stay safe and do good in the city.
One interesting fanfiction could be about Momonga in a modern human world, facing the challenges of adapting to a completely different society. He might use his unique skills and knowledge from the game world to solve modern problems, like dealing with technology that is both fascinating and confusing to him.
He could develop more empathy towards humans. Since he's in human form, he gets to experience life from their perspective. This could make him more understanding and less likely to use his powers recklessly.
There could be a plot where Bella is initially horrified by her love for human blood but gradually succumbs to it. Maybe she starts to have dreams or visions that fuel this desire. It could also be that she discovers a secret society within her world that is centered around this concept of loving human blood, and she has to decide whether to join or fight against them. Also, her relationships with other characters like her love interests would be greatly affected, leading to a lot of drama and conflict.
A plotline might involve the organic human being in danger, and Bumblebee comes to their rescue. This leads to the human becoming intrigued by Bumblebee and wanting to learn more about his world. As they interact more, they face challenges together, such as dealing with other Transformers who might not trust the human. The story could revolve around them proving that their friendship can be a valuable asset.
One possible plotline could be that Jack Sparrow is a shapeshifter. He might change into different forms to escape from his enemies or to gain access to hidden treasures. For example, he could transform into a seagull to spy on other pirate ships.
Momonga would also face challenges in terms of adapting to the human lifestyle. He has to deal with things like finding shelter, getting food, and maintaining his health. In the game world, these aspects were not really relevant in the same way. He might not even know how to cook or find a proper place to live. And he would have to learn about money and how the human economy works, which is a whole new and complex system for him.