A plot could be centered around a young psychiatrist who comes to Arkham to study the inmates, specifically Scarecrow. She tries to understand his psyche but ends up getting caught in one of his elaborate fear - based schemes. This could lead to Batman having to rescue her while also facing his own fears that Scarecrow has exploited.
Perhaps a plot where Scarecrow somehow gains control of Arkham Asylum completely. He turns it into his own personal fear - ridden domain and Batman has to infiltrate it alone. Along the way, he encounters other inmates who have been turned into Scarecrow's minions by the fear toxin, and he has to use his wits and combat skills to reach Scarecrow and stop his reign of terror.
One idea could be exploring Scarecrow's backstory in more depth. Maybe show his early days in Arkham Asylum, how he was treated by the staff and inmates, and what led him to become the terrifying Scarecrow. Another plot could involve Scarecrow creating a new and more powerful fear toxin that not only affects Batman but also the citizens of Gotham, and Batman has to race against time to find an antidote while dealing with his own fears.
Another plot could involve a crossover with a fantasy world. Imagine Batman being transported to a world like Middle - earth. He'd have to use his gadgets and combat skills in a world full of magic and mythical creatures. He might team up with characters like Aragorn or Legolas to fight against an evil force that has some similarities to the criminals in Arkham Asylum, perhaps a dark sorcerer who is as mad and unpredictable as the Joker.
One idea could be inserting yourself as a new inmate with a unique skill set, like being a master of disguise. You could use this to outwit the villains and even Batman at times. Another could be being a doctor who has a secret agenda and is using the chaos in Arkham to further their own ends. Maybe you're trying to steal some of the Joker's toxin for your own evil plan.
Perhaps a fanfiction where Poison Ivy falls ill due to some strange new chemical in Arkham Asylum. Batman, instead of seeing her as just a villain, decides to help her find a cure. This would lead to a journey through the asylum, facing other villains who might want to take advantage of Ivy's weakened state, and also a deeper exploration of Ivy's character and her connection to nature.
A crossover with the Justice League. Imagine if a mind - controlling villain took over Arkham Asylum and used the inmates as a weapon against the Justice League. The League would have to infiltrate the asylum, not only fighting the villains but also trying to break the mind control without harming the inmates too much.
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.
For Scarecrow's character description, start with his physical presence. He moves in a jerky, almost inhuman way, like a puppet on strings. His hands are bony and claw - like. His eyes, which can be glimpsed through the holes in the sack, are filled with a manic glint. In terms of his character, he's obsessed with fear. He sees it as a tool, a weapon, and a form of art. He has no qualms about using it on anyone, whether they're a criminal or an innocent.
Well, a great plot for Spider - Man Arkham Asylum fanfiction could be that the Green Goblin somehow gets locked in Arkham. Spider - Man follows him there to finish their feud once and for all. But when he arrives, he discovers that the asylum's strange atmosphere is affecting his powers in unexpected ways. He has to rely on his wits and some newfound allies among Arkham's inmates to defeat the Goblin and escape. This would create a lot of interesting scenarios as Spider - Man tries to navigate the dangerous and unpredictable world of Arkham Asylum.
A really interesting plot twist could be that the Grimm from RWBY are somehow connected to the madness in Arkham Asylum. Maybe they are being summoned by one of the inmates who has some sort of dark magic. Another plot twist could be that a character from RWBY, like Yang, turns out to be related to one of the Arkham Asylum staff in a very unexpected way.
One idea could be exploring the backstories of the lesser - known characters in the 'Batman Assault on Arkham' universe more deeply. For example, you could focus on Killer Croc's life before Arkham and what led him to become the way he is. Another plot could involve a team - up between unexpected characters from the movie, like Harley Quinn and Deadshot, against a new threat in Arkham that the Bat - family is unaware of.