What could a 'Tony Stark is an Atlantis' fanfiction be about?

Yes, there might be. There are countless fanfiction stories out there that combine different fictional universes. Writers often like to create crossovers where characters from one world, like Tony Stark from the Marvel universe, are placed in the context of another, such as Atlantis. You can try searching on popular fanfiction websites to find such stories.

It could be about Tony using his scientific mind to understand the Shinigami powers. Maybe he tries to reverse - engineer their abilities or find a way to incorporate them into his Iron Man suit. For example, he might study how Shinigami can move between the living world and the afterlife and try to create a device that allows him to do the same.

It could be about Tony Stark finding a way to integrate magic into his technology. Maybe he discovers a magical energy source and figures out how to use it in his Iron Man suits to give them new abilities.

Pepper Potts could be a big help. She knows Tony so well, and she could try to jog his memory by showing him things from their past together, like pictures or mementos. Rhodey could also be there for him. He could tell Tony stories about their military days and how they became friends, which might trigger some memories.

Perhaps the plot twist is that Gregory Stark is from an alternate universe where the rules of physics and technology are different. His methods of saving Tony Stark seem strange and dangerous at first, but in the end, they lead to a revolutionary breakthrough in both Stark's personal technology and the way the world views superheroes.

One reason could be that he's frustrated with the leadership or the direction the Avengers are taking in the fanfiction. He might feel his ideas are not being heard.

One possible storyline could be that the child inherits Tony's genius. The child might start showing an aptitude for engineering at a very young age. Maybe they'd start tinkering with small gadgets in the Stark workshop, and Tony would be both proud and a bit worried about the child getting into dangerous stuff. Another could be that the child has to deal with the pressure of being Tony Stark's offspring in a world full of superheroes and villains. People might have high expectations or target the child because of who their father is.

One reason could be the loss of a close friend like Steve Rogers. Their complex relationship and the times they fought side by side, if Steve were to sacrifice himself, it would be a huge blow to Tony. He might cry out of grief and also regret for the times they had disagreements.

One possible plotline could be Tony Stark struggling to manage his diabetes while also dealing with his superhero duties. For example, he might have a low blood sugar episode during a fight, which could put him at risk. Another could be his journey in finding a cure or better treatment for his diabetes using his scientific genius.

In a Tony Stark retires fanfiction, he might focus on his family. He could spend more time with Pepper and their kids, passing on his knowledge of technology in a more personal way, like teaching his kids how to build simple robots. Also, he might start a foundation dedicated to using clean energy technology for the betterment of the world.