There is a forest that has always been avoided by the locals. It is said that within the forest, there are trees that can move and voices that whisper disturbing things. A group of hikers decides to explore the forest. As they enter, they are gradually separated. Each hiker then experiences a series of terrifying illusions related to their past traumas. The forest seems to feed on their fear and pain.
A dark fantasy story could revolve around a cursed forest. Legend has it that anyone who enters the forest is never seen again. The protagonist, a brave knight, enters the forest to find his lost love. Inside, he discovers that the forest is a living entity filled with twisted trees and strange, malevolent spirits. He has to face his own inner demons as well as the physical threats of the forest to find his beloved.
You could start with a character who has a dark past that they are trying to hide. For example, they might have committed a crime long ago. Then, slowly introduce elements that make them suspect that someone is onto them. This creates suspense as the reader wonders if they will be caught.
Good ideas for a long dark custom story can come from different aspects. For instance, you could base it on a post - apocalyptic scenario where the world has been changed by some unknown disaster. The main character could be a scientist trying to find a cure for a strange illness that is spreading among the survivors. Or perhaps a story about a group of outcasts who find an abandoned town and try to make it their own, facing not only the elements but also other hostile groups. You can also play with the concept of time travel, where a character from the present is sent back to the time when the world started to go dark in the game's lore.
A simple idea is a hiker gets lost in a dark forest at night. They keep hearing strange howls in the distance. As they walk, they come across a clearing where there is a large, old tree with a noose hanging from it. Suddenly, they see a pair of glowing eyes in the bushes. It could be a werewolf or some other dark forest creature that hunts at night.
One main idea could be the concept of secrecy. Civilizations keep themselves hidden to survive.
One idea could be a world where a powerful dark sorcerer has cursed the land, causing eternal night. The only hope lies in a young outcast with latent magical powers who must journey through a haunted forest filled with demonic creatures to find the sorcerer and break the curse.
Perhaps they are living in a parallel universe where everything is dark and gloomy. Dark Naruto and Dark Kushina could be trying to find a way to break through to the normal universe. They might encounter strange versions of their friends and foes, and have to battle their own inner demons along the way. For example, Dark Naruto might struggle with the darker aspects of the Nine - Tails' power that he has fully embraced in this universe.
You could write a 'the dark crystal fanfiction' about a Skeksis who has a change of heart. Perhaps this Skeksis realizes the error of their ways after seeing the destruction they've caused. They then try to secretly help the Gelflings, all while hiding their new - found compassion from the other Skeksis. This would add an interesting layer of drama and conflict to the story.
One idea could be exploring a different ending for the story. Maybe the main characters find a new way to defeat the evil forces that was not shown in the original. Another could be a time - travel based fanfiction where a character goes back in time to change certain events that led to the current situation in Dark Shadows 2.
You could create a fanfic where the protagonist teams up with one of the enemies in the game. For example, they make a deal with a particular monster to escape the maze together, with each having their own motives and secrets.