Gwen would be a great character to pair with Alien X. Her magical abilities could complement Alien X's powers in interesting ways. For instance, when facing a threat that requires both brute omnipotent force and the finesse of magic. Another good pairing could be Kevin. His ability to absorb and use different forms of energy could interact with Alien X's power source in unexpected ways, like when they need to combine their powers to break through a powerful energy barrier.
Power and responsibility is also a big theme. Ben has to handle the powers of his alien forms responsibly, especially when dealing with aliens. In many fanfics, there's also the theme of discovery. Ben discovers new things about the aliens, their cultures, and their abilities. For example, he might learn a new power from an alien that he can use in a different way. There's also the theme of cooperation, where Ben and the aliens work together to achieve a common goal, like saving a planet or stopping a powerful enemy.
One idea could be exploring Alien X's internal conflict between Bellicus and Serena in a new situation. For example, when faced with a moral dilemma on a planet where two species are at war and both have valid reasons for their actions. Another plot could be Alien X having to deal with a powerful new enemy that can somehow disrupt his omnipotent powers. Maybe this enemy has the ability to split Bellicus and Serena's consciousness further, causing chaos within Alien X.
Well, it depends on how it's written. If it focuses on positive aspects like friendship, adventures, and character development within the Ben 10 universe, it can be appropriate. However, if it involves inappropriate or adult - themed content, then it's not acceptable, especially in a public or general - audience context.
Ben Tennyson is the central character. He has the ability to turn into various ultimate aliens, which is a big part of the story. Gwen Tennyson, his cousin, might also be a main character as she has her own powers and often helps Ben. And then there could be Kevin Levin, who has powers related to absorbing matter. These three characters often work together to face the threats in the 'Ben 10: Ultimate Alien' universe.
One idea could be exploring the backstories of the aliens more in - depth. For example, how did Four Arms become so strong? Another could be a story where Ben has to team up with his enemies to fight a greater threat. Maybe Vilgax and Ben have to work together against an even more powerful alien race.
Heatblast is really cool. He can generate and control intense heat, which makes him great for combat and for melting things. He has a flaming body which gives him a very intimidating look.
Well, there's 'The Alien Bond'. In this fanfic, Ben Tennyson forms a very special bond with an alien that has the power to manipulate time. It's really interesting as it shows how their relationship develops and how they use their combined powers to face various challenges. There are also some fanfics that explore what would happen if Ben could communicate with his alien forms on a more personal level, like in 'Ben and the Sentient Aliens' where the aliens have their own personalities and thoughts that Ben has to deal with.
Fourarms is really cool. He's big and strong with four arms, which gives him great power in combat. Heatblast is also amazing as he can generate and control fire.