One great 'Batman Arkham Asylum' fanfiction is 'The Dark Knight's Redemption'. It delves deeper into Batman's psyche as he battles his inner demons while trying to escape the asylum. The author does a great job of capturing the dark and gritty atmosphere of the game.
First, know the source material well. Understand the characters, the setting of Arkham Asylum, and the overall mood of the game. For example, Batman is a complex character with a dark past, so make sure to capture that in your writing.
A more complex fanfiction could involve all of Team RWBY in Arkham Asylum. Blake could use her stealth skills to move around unnoticed, Yang's strength would be useful in physical confrontations. They could be there because some powerful enemy has lured them there, thinking it's a place where they'll be weakened. But together with Batman and some of the inmates who might side with them (like Harley Quinn who has a complex sense of morality), they could turn the tables on the enemy.
One idea could be that Naruto is somehow transported to Arkham Asylum. He might initially be confused by the strange new world, but his ninja skills could come in handy. For example, he could use his speed and agility to avoid the traps and villains in the asylum. Maybe he teams up with Batman, who is intrigued by Naruto's unique abilities.
The plot involves Batman being lured into Arkham Asylum by the Joker. Once inside, he discovers that the inmates have taken over and he must fight his way through them. There are also sub - plots about the history of the asylum and the mental states of the villains, making for a complex and engaging story.
One example could be a story where characters from RWBY end up in Batman Arkham Asylum. Maybe Ruby and her team are trying to find a way out while also encountering some of the well - known villains from the Batman universe. Another could be a crossover where Batman characters are brought to the RWBY world and have to adapt to the Grimm - filled environment.
How about Gollum from Lord of the Rings? It seems really odd at first, but think about it. Gollum's sneaky nature and knowledge of dark places could be useful in Arkham Asylum. Batman could try to control Gollum's greed and use his skills to navigate the more dangerous parts of the asylum. And Gollum might be fascinated by Batman's shiny gadgets. It would be a very strange and interesting dynamic.