Another theme might be redemption. After the betrayal, the story could explore whether the guardian tries to make amends or if Ash ever forgives them. It could also be about the journey of the guardian to regain their lost honor or position in Ash's life.
One great aspect of Aura Guardian Ash fanfiction could be the exploration of Ash's latent aura powers. Maybe in these stories, Ash discovers he has a much deeper connection to the aura realm than he ever knew. This could lead to him having new abilities and forming unique bonds with Pokémon that are also attuned to the aura.
Well, you can try looking on some popular fanfiction websites like Archive of Our Own. Just search for 'ash aura guardian betrayed' there, and you might find some interesting stories.
Perhaps the aura guardian was mind - controlled. An evil force took over its mind and made it act against Ash. In this case, the story could revolve around Ash trying to break the mind - control and save his friend. It would involve a lot of action and mystery as Ash figures out what's wrong and how to fix it.
Maybe an ancient evil spirit that has a vendetta against Ash. The spirit could possess the aura guardian and make it turn against Ash. In this scenario, the main antagonist is not really the guardian but the spirit that controls it, and the story would be about Ash fighting this spiritual evil.
It depends on your personal taste. If you're a big fan of the Aura Guardian concept and like stories centered around Ash, it could be a great read. Some fanfictions really capture the essence of the characters and expand on the lore in interesting ways.
It could be that there is a young, impressionable character who looked up to Ash Aura. After the betrayal, this character is confused and starts to question his own beliefs. There might also be a powerful mage in the story who has the ability to see the truth behind Ash Aura's actions and is trying to prevent the chaos that the betrayal has caused.
In some Aura Guardian Ash fanfiction, Ash could be part of a prophecy. As an Aura Guardian, he might be the key to saving the Pokémon world from a great threat that is related to the disruption of the aura. This would put him in a position where he has to make sacrifices and grow in ways he never expected, all while relying on his newfound aura abilities.
Well, it could be that Ash Aura, who was perhaps trusted by the group in the fanfiction world, reveals some dark secrets or joins the enemy side, thus betraying those who once relied on him. Maybe he was lured by power or some hidden motives.
In 'ash the last aura guardian fanfiction', a frequently seen theme is friendship. Ash's friends play an important role in his journey as the last aura guardian. They support him, and together they face challenges. Also, the theme of redemption can be present. Maybe Ash has to make up for past mistakes while being in this new role. And there's often a theme of power growth, as he gradually becomes more proficient in using his aura guardian abilities.