If Ash starts with a legendary pokemon such as Rayquaza, it could be that there are abnormal weather patterns in the Pokemon world. Rayquaza has the ability to control the weather. Ash and Rayquaza team up to figure out what is causing these extreme weather changes. Along the way, they meet other trainers who are also affected by the weather problems. Ash has to prove that he is worthy of having a legendary pokemon by using Rayquaza to restore balance to the weather.
Well, in this case, a fanfiction being 'legendary' might mean that it gives Ash a very special role. Maybe he's the chosen one to unlock some hidden power of the legendary Pokémon. It could also be about the settings. If it's set in a long - lost, mythical land full of secrets and ancient powers related to the legendaries, that would contribute to it being a 'legendary' fanfiction. The plot could involve Ash facing challenges that are on a scale never seen before, like battles against multiple legendary Pokémon at once or trying to prevent a cataclysmic event that only he can stop because of his connection to the legendaries.
The appeal lies in seeing Ash in new and exciting situations. With legendaries involved, his journey becomes more epic. It's like taking the underdog story of Ash in the anime and supercharging it.
In Ash-centered legendary Pokemon fanfiction, often Ash has extraordinary adventures. He might form unique bonds with legendary Pokemon that are not seen in the official storylines. For example, he could befriend a Mewtwo and together they face off against an evil organization trying to clone more powerful Pokemon. These fanfictions allow for a lot of creativity, expanding on Ash's character and his relationships in the Pokemon world.
There are also fanfictions where Ash catches Rayquaza. This could be set during a time when the sky is in chaos due to some dark energy. Rayquaza is drawn to Ash because of his pure heart and determination. Ash, with his usual courage, teams up with his pokemon to assist Rayquaza in restoring balance. As a result, Rayquaza allows Ash to catch it.
Articuno, Zapdos, and Moltres are quite common. Their elemental powers and the mystery surrounding them make for great fanfiction material. Ash might encounter them during his travels and have to either help them or face off against them in some way.
One of the Legendary Pokemon could be Giratina. Despite its somewhat dark and otherworldly nature, Giratina might be intrigued by Ash's light - heartedness and his ability to make friends with all kinds of Pokemon. Dialga and Palkia could also be part of the harem. Dialga, with its control over time, might see Ash as an important factor in the future of the Pokemon world. Palkia, in charge of space, could be interested in how Ash navigates different regions and spaces in his journey. And don't forget about Ho - Oh. Ho - Oh is a symbol of hope and might see Ash as a bringer of hope in the Pokemon world, thus joining his harem.
Arceus is quite popular. Given that it's considered the creator of the Pokemon universe in the official lore, it often has a significant role in fanfictions. Mewtwo is also very common. Its powerful psychic abilities and complex backstory make it a favorite for fanfic writers to explore. Another popular one is Lugia. With its majestic appearance and its connection to the sea, it's often a central figure in many stories.
Often, Ash has to complete a quest. In a fanfic with Ho - Oh, Ash might have to find three special feathers scattered across the region. These feathers are said to be the key to summoning Ho - Oh. As he embarks on this journey, he faces many challenges and overcomes them with his existing Pokemon team. Once he collects all the feathers, Ho - Oh appears and, impressed by Ash's determination, decides to fight alongside him. Another way is through a prophetic vision. Ash might have a dream that tells him how to find and bond with a Legendary like Entei, and he follows this vision to make it happen.
Well, other trainers would probably be both jealous and in awe. Some might try to befriend Ash just to get closer to the legendary pokemon. Others, especially those with a competitive streak, would see Ash as a huge threat and might be less friendly towards him.