One great 'Dark Shadows' and 'Twilight' fanfiction might be one that combines the gothic elements of 'Dark Shadows' with the supernatural romance of 'Twilight'. For example, a story where a character from 'Dark Shadows' visits Forks and gets involved in the vampire - human drama there. Another could be a story that explores how the different vampire rules in both universes interact when characters cross over.
First, you need to be familiar with both universes. Read the original works, watch the shows or movies. Then, think about the characters you want to use. Decide if you want to create a new character that will interact with the existing ones. For example, a new vampire who is a hybrid of the 'Dark Shadows' and 'Twilight' vampire types.
Well, it could be a new vampire that the author has created. This vampire might be a loner, living in the shadows away from the main vampire clans in Twilight. Another could be a human character who stumbles upon this hidden vampire world.
It could be about a mysterious and dangerous character in the Twilight universe who lurks in the shadows. Maybe it's a new vampire or some other supernatural being that poses a threat to the main characters in the Twilight world.
Perhaps it's a human who has somehow discovered the existence of vampires and werewolves and has decided to take matters into his own hands, using his knowledge of the town's layout and the creatures' weaknesses to become a killer in the shadows. He might be motivated by a desire to protect the town from what he sees as a threat, but his methods are extreme.
Another theme is the battle between good and evil. In the 'Dark Shadows 1991' fanfiction, writers often create new scenarios where the characters have to face more intense battles between the forces of good and evil, adding more drama and action to the stories.
One great 'Dark Shadows' fanfiction is 'The Return of Barnabas'. It delves deeper into the character of Barnabas and his struggle with his vampiric nature in a new and interesting way. Another is 'Victoria's New Adventure' which takes the character of Victoria on a journey that was not explored in the original series. And 'The Darker Side of Collinwood' shows a different perspective of the famous Collinwood estate, filled with mystery and intrigue.
I would recommend 'Darkness Unleashed in Supernatural's World'. This fanfiction delves deep into the darker aspects of both universes. It creates a unique story where the entities from Dark Shadows start to infiltrate the Supernatural world. The writing style is quite descriptive, making it easy to visualize the events.
Perhaps a plot where a werewolf, instead of being an enemy of vampires in the Twilight universe of this fanfiction, forms an alliance with a vampire living in the shadows. They work together to protect their territory from a common threat that the Cullens are unaware of.
The unique blend of the Yugi universe with the concept of twilight shadows. It's not something you see in the original series often. The fanfiction writers get to explore new, darker aspects of the characters and their world.