In some fanfictions, Scarecrow is often depicted as a formidable foe to Batman. His fear toxins play a major role. Batman has to constantly overcome the extreme fears that Scarecrow induces. For example, in certain stories, Scarecrow may target Batman's deepest traumas, like the death of his parents, and use that to try and break him. This creates a very intense dynamic where Batman has to rely on his willpower and detective skills to outwit Scarecrow.
Scarecrow horror stories create fear through their appearance. Scarecrows are often depicted as human - like figures with tattered clothes and empty faces. This resemblance to humans but lack of humanity is spooky. For example, in many stories, the scarecrow's blank eyes seem to stare into your soul.
One popular theme is the exploration of fear. Since Scarecrow is the master of fear, fanfictions often delve deep into how different characters, especially Batman, experience and overcome fear. Another theme is the battle of wits. Batman is a brilliant detective and Scarecrow is a cunning adversary, so their mental duels are a big draw.
One interesting fanfiction could be about Scarecrow's origin in the 'Batman Begins' universe. It might explore his early experiments with fear toxins in more detail than the movie did.
One possible plot twist could be that Poison Ivy decides to protect Batman's secret instead of using it against him. Maybe she realizes that Gotham needs Batman more than she needs revenge or chaos at that moment.
There's a story of a group of kids who dared each other to spend the night in a field with a creepy old scarecrow. As the night fell, they started to feel uneasy. One kid swore he saw the scarecrow's eyes glow red. They all huddled together, trying to ignore it. But then they heard strange rustling sounds coming from the direction of the scarecrow. They were so scared that they ran all the way home, not looking back once.
In this fanfiction scenario, Poison Ivy may initially be angry. She might feel betrayed if she had some sort of relationship with either Bruce Wayne or Batman before. She could also be a bit jealous, thinking that Batman has been hiding this huge part of himself from her. However, on the other hand, she could also be impressed by the lengths Bruce goes to protect the city. This new knowledge could lead to a whole new dynamic between her and Batman, with her either becoming an ally or an even more dangerous foe, depending on her motives and the events that unfold in the fanfiction.
The moral might be about acceptance. The scarecrow, which was an inanimate object in a way, was accepted by the other characters in the story. For example, the birds accepted it as a friend or the girl treated it kindly. It shows that we should accept others for who they are, no matter how different they seem.