Well, a great plot for X Men Apocalypse fanfiction could be a love story between two mutants who are on opposite sides during the Apocalypse chaos. Or perhaps a story where a group of new mutants, not part of the main X - Men group, band together to take on Apocalypse in their own unique way. You could also do a fanfic where Apocalypse actually wins and then see how the remaining mutants survive and resist under his tyrannical rule.
One idea could be exploring the backstories of the minor mutants more. For example, how did they discover their powers before the events of Apocalypse. Another could be a time - travel fanfic where a mutant goes back in time to stop Apocalypse from ever rising to power. Maybe also a fanfic about the mutants trying to adapt to a post - Apocalypse world and rebuilding society in a more mutant - friendly way.
A cool X Men Apocalypse fanfiction could focus on the psychological impact on the mutants. Like how they deal with the fear and trauma during the Apocalypse. You could also write about a mutant with a very unique power that was overlooked by both the X - Men and Apocalypse, and how this mutant ends up being the key to the whole situation. And then there's the idea of a fanfic where the mutants form an alliance with some humans to fight against Apocalypse, exploring the relationship between the two species during this extreme situation.
Another idea is a crossover with the Star Trek universe. The X - Men could find themselves on a Starfleet ship. They might have to deal with the differences in cultures and technologies while also trying to stop Apocalypse from spreading his chaos across the galaxy.
One idea could be that Harry has a unique mutant power that Logan initially misunderstands. For example, Harry might be able to manipulate time in small increments, which Logan mistakes for some form of trickery at first. Another could be that they team up to rescue a group of young mutants from a powerful anti - mutant organization. They would have to combine Logan's combat skills and Harry's strategic thinking to succeed.
A cool plot could be that a new, extremely powerful mutant emerges who has the ability to control all forms of energy. This mutant's powers are so great that they start to disrupt the fabric of reality. The Avengers and the X - Men both realize that this mutant needs to be controlled or taught to manage their powers. However, different factions within both groups have different ideas on how to approach the situation. Some want to be more forceful, while others believe in a more diplomatic approach. This leads to internal conflicts within the combined group as they also battle external threats caused by the mutant's out - of - control powers.
One idea could be that Superman is somehow transported to the X - Men's universe. He teams up with the X - Men to fight a common enemy like a powerful mutant who has the ability to nullify Superman's powers on a large scale. They have to figure out how to combine their skills and powers to overcome this threat.
One idea could be that the kryptonite in Smallville starts to affect the mutants in strange ways. Maybe it suppresses or enhances their powers in unexpected manners. For example, Wolverine's healing factor could be slowed down by kryptonite exposure, leading to a real threat when he gets injured. Another plot could involve Lex Luthor getting his hands on some mutant DNA and trying to create his own super - soldiers, which would draw the attention of the X - Men. They could team up with Clark Kent to stop Luthor's evil plans.
One plot idea could be that the One Ring somehow finds its way into the X - Men universe. Maybe Magneto senses its power and wants to use it for his own purposes, believing it could give him ultimate control over mutants and humans alike. The X - Men, on the other hand, realize the danger of the Ring and try to stop Magneto from getting his hands on it. Another idea is that some of the LOTR characters are reincarnated as mutants. For example, Aragorn could be a mutant with enhanced leadership abilities and physical prowess, and he teams up with the X - Men to fight a common enemy that threatens both Middle - earth and the mutant world.
One idea could be that the X - Men and Spiderman team up to fight a common enemy like Magneto who has joined forces with some of Spiderman's foes, such as Doctor Octopus. They'd have to combine their powers and skills to take on this powerful alliance.
One plot idea could be Pietro and Wanda exploring their powers further in a world that fears them. They might have to team up with other X - Men to face a new, powerful mutant - hating organization. Another could be a story set in an alternate universe where they have different relationships with the other mutants. For example, Pietro could be more of a loner and Wanda has to convince him to work with the team.
The OC could be a mutant from a different country who comes to the X - Men school. Pietro is immediately intrigued by her different culture and way of using her powers. They start to exchange stories about their mutant experiences, and a relationship forms based on mutual understanding and respect for their differences.
One plot idea could be that the OC is a new mutant at the school and Kurt is assigned to show them around. They start off as friends but gradually develop deeper feelings as they face challenges together, like dealing with a bully mutant. Another could be the OC has a special power that Kurt needs to help control, and in the process, they bond over their shared experiences of being different.