A plot could revolve around a mystery in the dark. For example, strange disappearances are happening only at night in the shadows. The protagonist has to figure out what's causing it, whether it's a supernatural being or a secret organization using the cover of darkness.
One idea could be a character discovering a hidden power within the shadows that they must learn to control. Maybe they are initially afraid of it but then realize it can be used for good.
Perhaps the fanfiction could focus on a group of friends who get lost in a shadowy, enchanted forest. As they try to find their way out, they encounter various challenges and strange creatures that lurk in the shadows, and they must rely on each other to survive.
Another plot idea is to create an alternate timeline within the 'a walking shadow' world. This could involve different events happening to the characters, leading to new relationships and challenges. For example, a character who was once an enemy could become an ally in this new timeline.
For Shadow of the Colossus fanfiction, you could write about a hidden society within the Forbidden Land. They worship the colossi in a different way than the main narrative implies. Wander stumbles upon this society during his journey. Or, you could do a fanfic where the colossi are not actually the 'bad guys'. They are guardians of something far more important and Wander is being used by the shadowy forces that sent him on this quest. And finally, a story about how the magic or energy that powers the colossi affects the wildlife in the Forbidden Land in ways not shown in the game. For instance, there could be mutated or super - intelligent animals due to this energy.
One idea could be a dark Supergirl who is corrupted by a powerful, evil force from outer space. She starts using her powers for her own gain, causing chaos in Metropolis. Another could be a Supergirl who has lost faith in humanity due to some great betrayal and turns to a darker path to 'teach' humans a lesson. And a third idea might be a Supergirl from an alternate, darker universe where her powers are more unstable and she has to constantly battle her inner demons.
Perhaps a story where a secret society meets only in the dark of night. The main character stumbles upon their meeting and gets drawn into a world of secrets, power struggles, and ancient rites.
One idea could be exploring the origin of the 'whispers' in a more in - depth way. Maybe the whispers are the voices of long - lost souls trapped in a parallel dimension. Another plot could involve a character who is the only one able to hear the whispers clearly and has to figure out how to stop them from driving people mad. Or perhaps a story where the whispers are actually a form of ancient magic that has been misused, and the main character has to set things right.
Perhaps a fanfiction could focus on the backstory of Harvey Dent before he became Two - Face. It could show his early days as a prosecutor and how his idealism gradually got corrupted, which would add more depth to his character in the Dark Knight universe.
One idea could be exploring Dark Seraphina's origin. Maybe she was once a normal angel but something tragic happened that turned her dark. Another could be a story where she teams up with an unlikely ally, like a human with special powers, to fight a common enemy. It could also be interesting to write about her trying to redeem herself.
One idea could be Ahsoka being corrupted by the dark side due to a powerful Sith artifact she discovers. She starts to use her skills for her own gain, causing chaos in the galaxy. Another could be her being manipulated by a hidden Sith Lord who convinces her that the Jedi way is wrong. Maybe she forms her own dark order, recruiting those who feel betrayed by the Jedi or the Republic.
One idea could be that Spider - Man has to face a new villain who has the power to manipulate his darkest fears and turn them into reality. Another could be a version where Spider - Man is wrongly accused of a major crime and has to clear his name while also dealing with the city turning against him.
A plot could involve a group of dark digimon forming an alliance to take over a particular area of the digital world. They start by targeting the weakest digimon settlements. The story could follow a young digimon trainer who tries to gather allies to fight back against this dark alliance. There could be many challenges along the way, like finding rare and powerful digimon to join the cause, and also dealing with the psychological warfare that the dark digimon use. For example, they might spread false rumors to cause distrust among the good digimon.