Well, for Toxapex in the story, I'd say a great moveset is Venoshock, in addition to Recover, Toxic Spikes, and Haze. Venoshock deals more damage when the target is poisoned, which pairs well with Toxic Spikes. Recover, of course, is there to keep Toxapex alive. Haze can be used to clear out any stat changes on the field, which can be really handy in certain story battles.
In this fanfiction, it could be that Ash has a really good strategy. He might first make Gyarados use up a lot of its energy by making it attack Charmander's illusions or decoys. Then, when Gyarados is tired, Charmander can step in with its full power. Charmander could also use the environment to its advantage. Maybe there are some flammable objects around that can be set on fire by Charmander, creating a more powerful and widespread fire attack that Gyarados can't avoid.
One effective moveset for Cofagrigus could be Shadow Ball, Will-O-Wisp, Protect, and Toxic. These moves give it a mix of offensive and defensive capabilities.
One common theme is empowerment. Female Gyarados are often depicted as strong and independent, breaking free from constraints. For example, in many stories, they might not conform to the typical behavior expected of Pokémon in their species. Another theme is friendship, like forming unique bonds with trainers or other Pokémon. This shows that despite their power, they also value connections.
A lot of these fanfictions might have a theme of discovery. The female human discovers the unique abilities and nature of Gyarados. There could also be themes related to protection, where the Gyarados protects the female human from danger, or vice versa. Sometimes, there are themes of mystery, like uncovering secrets about Gyarados that no one else knows.
There could be a fanfiction where Ash catches the Red Gyarados during a special event in a mysterious lake. In this story, the Red Gyarados might be seen as a symbol of power and Ash's catching it could be a turning point in his journey, leading to new adventures and challenges.
Well, 'The Mysterious Female Gyarados' is another great one. It's set in a more mysterious region where the female Gyarados is seen as a sort of enigma. The plot unfolds as various characters try to understand her powers and her origin. It's full of suspense and interesting twists.
It could be about Ash finding a Gyarados in an unexpected place, like a hidden lake in a forest. Then he tries to train it and form a bond with it, facing challenges along the way.
You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just type in 'Ash Gets a Gyarados' in the search bar and see what comes up.