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 possible fanfiction could focus on a team - up between Poison Ivy and another Arkham character, like Catwoman. They could form an unlikely alliance to take on a common enemy in Arkham City. The story could show their different motives and how they manage to work together despite their differences. For example, Ivy wants to protect the natural environment of Arkham City which is being destroyed by a new construction project, while Catwoman is more interested in the valuable artifacts hidden in the buildings.
In Arkham Asylum, Poison Ivy's character can be studied through her interactions with the other inmates and the guards. Does she use her charm or her powers to get what she wants? How does she react to the restrictions placed on her? You could also look at her backstory and how her experiences led her to become the plant - loving villain. Maybe she was mistreated in the asylum in the past, and that fuels her current actions. Write about her emotions, her hopes (if any) for a better world for plants, and her despair at the state of the environment outside. This all helps in creating a well - rounded character study.
There are fanfictions that explore Poison Ivy's backstory in the Arkham Knight world more deeply. For example, a story might focus on her early days and how she came to have such a strong connection with plants. This can add a lot of depth to her character in the context of the game's lore.
One possible fanfic could be centered around Batman's encounters with Poison Ivy within the Arkham universe. Maybe it could explore their complex relationship, with Batman constantly trying to stop Ivy's environmental extremism while also seeing the good in her intentions at times. For example, Ivy might be trying to protect a particular area in Arkham City that she believes is crucial for nature, and Batman has to find a way to balance the law and her motives.
One plot could involve Poison Ivy being kidnapped by a new, unknown villain in Arkham. This villain wants to use her powers for their own evil plans. Batman then has to team up with some of Ivy's plant minions (who have a limited form of sentience) to rescue her. During the rescue, we could see a different side of Batman as he tries to understand and communicate with the plant creatures.
Another popular theme is her relationship with Batman. Sometimes it's a romantic relationship, other times it's a begrudging alliance. Writers like to explore how two such different characters interact and what they can learn from each other.
A plot idea could be that Poison Ivy creates a new type of plant - based virus in Arkham that only affects humans who are harming the environment. Batman has to find a way to stop the virus from spreading while also dealing with Ivy's strong beliefs. Another idea is that Ivy discovers a rare plant in Arkham that she believes can save the planet, but it's in a highly guarded and dangerous area. Batman and Ivy might have to work together to retrieve it.
Some writers depict their relationship as a love - hate dynamic. Batman is attracted to Poison Ivy's beauty and her passion for nature, yet he hates her criminal ways. For example, he might be constantly in a struggle between his feelings for her and his duty to stop her crimes.
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.