Create unique physical traits. Maybe an Ultra Beast has a hidden ability that is only visible when it's in a certain mood, like glowing patterns on its body. Also, you could give it a special way of moving, like floating in a spiral pattern instead of walking.
The Ultra Beast could completely change the direction of Ash's journey. It might introduce him to new regions or dimensions he has never explored before. For example, if the Ultra Beast has the ability to open portals, Ash could end up in places with new Pokémon species to discover and new challenges to overcome.
Ultra Beasts can fit into the Pokemon Hall of Origin story in a fanfic by being the guardians of the Hall. Maybe they were placed there by some ancient power to protect the secrets within. So when the protagonist tries to enter the Hall of Origin, they have to face these Ultra Beasts.
One idea could be a story where a trainer accidentally bonds with an Ultra Beast during an Ultra Wormhole event. The trainer has to learn to communicate with it and protect it from those who want to use it for evil purposes.
One unique way is to make Ultra Instinct a power that is passed down through generations in a hidden family line within the RWBY world. For instance, Blake could discover she has this heritage and starts to unlock Ultra Instinct. Another way is to have it be a power that is only accessible in a certain location, like a forgotten temple in the Ever After. Characters would have to journey there and face trials to gain Ultra Instinct.
Well, in a fanfic about the Pokemon Hall of Origin and Ultra Beasts, you can expect a wild adventure. The Hall of Origin is a very mysterious place in the Pokemon world. Ultra Beasts are strange and powerful creatures from another dimension. A fanfic might explore how a trainer gets involved with the Ultra Beasts near the Hall of Origin. Maybe they accidentally open a portal to the Ultra Beast's world while exploring the Hall. It could also show battles between the trainer's Pokemon and the Ultra Beasts, with unique strategies based on the Ultra Beasts' strange abilities.
The story behind Ultra Beasts is quite mysterious. They are said to come from alternate dimensions and have unique powers and characteristics.
The main characters would likely include the Ultra Guardians themselves. They are probably a group of trainers with special skills or abilities. There could be a leader among them, who is very experienced and has a deep knowledge of Pokemon.
Gladion can also be quite popular. His edgy and mysterious personality, along with his strong Pokemon, can add a lot of depth to fanfiction. He might be portrayed as having a tense relationship with the Ultra Recon Squad at first but then gradually warming up to them.
Lillie is often a popular character. In fanfiction, she might be given more in - depth storylines, such as her further exploration of her connection with the Legendary Pokemon. Maybe she discovers a new form of Nebby or has an adventure that reveals more about her family's past.
One aspect of Pokemon Sun and Moon Ultra Guardians fanfiction could be the character development. The Ultra Guardians in the original game have unique personalities and abilities. In fanfiction, writers might expand on their backstories, like how they came to be part of the Ultra Guardians. For example, they could explore the early training days of a character and how they overcame difficulties to be a competent guardian.