Perhaps an experienced trainer who has seen the Pokémon world before the undead invasion and is now using their knowledge to lead the fight. And their most trusted Pokémon, like a Pikachu or a Charizard, could also be main characters. There might also be a mysterious character who seems to have some connection to the origin of the undead problem, either as a potential ally or an enemy.
It could be about a Pokémon story in a post - apocalyptic or nightmarish undead - filled setting. Maybe Pokémon are facing some kind of undead threat, like zombified Pokémon or some dark force that turns the Pokémon world into a nightmare.
Obviously, Phione would be one of the main characters. It could also have a trainer as a main character, someone who is deeply concerned about Phione's well - being and is determined to help it out of the nightmare. Maybe there could be a wise old Pokemon, like an Alakazam, that has some knowledge about the nightmare realm and helps guide them through it.
I don't know for sure as I haven't read it. But it could be Twilight Sparkle and her friends like Pinkie Pie, Rainbow Dash, etc. Since they are the main characters in the My Little Pony series, they are likely to be involved in any fanfic related to it.
Obviously, Apollo Justice is likely to be one of the main characters. Given the name, it's centered around him. But it could also include other characters from the original series like Phoenix Wright, who might play a role in helping or hindering Apollo in this nightmare scenario.
Since we don't know the exact details of 'the gathering pokemon fanfic', the main characters could be a group of young and enthusiastic Pokémon trainers. They might be on a journey to become the best and this gathering could be a crucial part of their adventure. It could also feature some Pokémon with special personalities as sort of secondary main characters, like a Pikachu that has a unique ability compared to others. Another possibility is that there are some wise old Pokémon trainers who are the main characters, guiding the younger ones during the gathering.
It could be the challenger themselves. They are usually the central focus, with their own personality, goals and dreams. Maybe they have a rival who is also a main character, constantly competing with them.
The Akatsuki members are the main characters. They bring their own unique abilities and goals. For example, Hidan's immortality could play an interesting role in the Pokemon world. He might be more reckless in battles because he knows he can't die easily. Kisame, with his shark - like appearance, could have an affinity for Water - type Pokemon and be really strong in underwater Pokemon battles. These characters' interactions with the Pokemon and each other are what drive the story in an Akatsuki Pokemon Fanfic.
It could be Pikachu as a main character. Since Pikachu is one of the most popular Pokémon, it would be likely to be involved in the story, perhaps bouncing on the trampoline and having a great time.
Obviously, Cheryl is one of the main characters. She's the center of the fanfic's story. Depending on the plot, her Pokemon would also be important characters. For example, if she has a Pikachu, that Pikachu would play a role in her adventures.
It could be a young and ambitious trainer. This trainer is often the one who drives the story forward, seeking out Fatalis for various reasons like proving their worth or to protect their region.