One interesting storyline could be about Ben using his alien forms in new and creative ways to fight against a powerful, previously unknown villain in the Justice Era. For example, he might combine the powers of different aliens in unexpected combinations to overcome challenges.
Another possible storyline is that Ben discovers a dark secret about the Justice Era that threatens the entire universe. He then has to embark on a journey to not only expose the secret but also find a way to fix the problem. Along the way, he might face opposition from those who want to keep the secret hidden, and he has to use his wits and the power of his Omnitrix to prevail.
One interesting storyline could be Ben and Gwen having to face a new, powerful alien threat that they've never encountered before. They might have to combine their unique skills and powers to defeat it.
In the Justice Era Fanfic, there could be new main characters introduced specifically for this era. Maybe there's a young hero -in -training who looks up to Ben and wants to learn from him. This character could bring a fresh perspective and add new dynamics to the story. There might also be an alien character who has unique powers and a complex backstory, and they end up being an important ally or foe depending on the circumstances.
Another storyline could involve Ben facing off against a new villain who is specifically after the Biomnitrix. This villain might have his own set of powers that make him a formidable opponent. Ben would then have to figure out how to use the new aliens in the Biomnitrix to defeat this enemy. Maybe he has to team up with some of his old alien forms in creative ways.
A third interesting storyline might involve a secret alliance between a member of the Justice League and a villain that the Young Justice team discovers. This discovery then sets off a chain of events where the Young Justice team has to decide whether to trust the rest of the Justice League and how to handle this new information without causing a complete breakdown in the superhero community.
One interesting storyline could be Ben using his alien forms in a virtual gaming world to defeat a powerful digital virus. The unique combination of his real - world powers and the challenges of the game environment makes it exciting.
One interesting storyline could be about Ben exploring new alien forms that were previously unknown in the official series. Maybe he discovers a form that has unique powers that he has to learn to control quickly to face a new and powerful enemy.
One popular storyline could be Ben and Helen teaming up to fight a new, powerful alien threat that neither could handle alone. They combine their unique abilities, like Ben's alien transformations and Helen's skills, to save the day.
Some 'ben 10 omniharem fanfic' might explore how the omniharem affects Ben's growth as a hero. Maybe the relationships make him more empathetic or teach him new ways to use his alien forms in different social situations. In these fanfics, the interactions within the harem could lead to character development not just for Ben but also for the other members of the harem.
One possible plot could be that the Omnitrix gets malfunctioned and starts sending out energy signals that attract the attention of the Justice League. Ben, in his various alien forms, has to work with the League to figure out what's wrong with the Omnitrix and stop an evil force that is also drawn to the energy. For example, Vilgax could team up with some of the League's villains like Lex Luthor to take advantage of the situation.
Another interesting plot could be that a powerful villain creates a device that can steal powers. He targets both Ben's aliens and the Justice League members. Ben and the League have to find a way to stop the villain before they lose all their powers. They go on a wild adventure across different dimensions to find the parts needed to destroy the power - stealing device.