You could also try searching on Tumblr. There are many bloggers who are into 'Game of Thrones' fanfiction and might have reblogged or even written their own dark and powerful Jon Snow stories. Use relevant tags like #JonSnowFanfiction #DarkJonSnow to narrow down your search.
One common theme is his struggle with new - found power. In these fanfictions, Jon Snow often has to deal with the moral implications of his power, whether it's a new magical ability or a political power. Another theme is his relationships. His interactions with other characters, like Sansa or Daenerys, can change significantly when he becomes dark and powerful.
There are many ways fanfiction writers could incorporate Jon Snow and the Dark Sister. For example, the Dark Sister could be tied to Jon Snow's true heritage. Maybe it was hidden away waiting for him to claim it as a Targaryen. This could lead to new storylines where he uses the sword to fight against the White Walkers or in the battle for the Iron Throne.
The character of Jon Snow himself is a big draw. His complex personality, being a bastard yet having noble qualities, gives a lot of room for fanfiction writers to explore. In powerful fanfiction, they can expand on his relationships, like his bond with Ghost or his unrequited love for Ygritte. Also, his potential as a leader and his Targaryen heritage are exciting elements to play with.
There's this fanfiction titled 'Jon Snow and the Dragons'. It imagines a scenario where Jon Snow has a special connection with the dragons, perhaps due to his Targaryen blood. It's really exciting as it weaves a new narrative around his character and his potential role in the world of Westeros. Also, 'Jon Snow: The Savior of the North' is a great read, focusing on his efforts to protect the North from various threats.
One interpretation could be that the Dark Sister is a symbol of Jon Snow's destiny. It might be a sign that he is meant to play a much larger role in the world of Westeros. For instance, he could use it to unite the North and the South.
One of the top authors is Aria Blackwood. Her 'Dark Jon Snow' fanfictions are known for their in - depth character exploration. She really gets into Jon's head and shows how he could turn dark in a very believable way. Another great author is Grey Wolf. His stories often have complex plots that revolve around a dark Jon Snow, and he is excellent at creating a dark and gritty atmosphere.
There might be a fanfiction where Dark Jon Snow and Daenerys meet in a different scenario, like on a diplomatic mission. Jon, with his changed personality, tries to manipulate Daenerys for his own ends. However, Daenerys is no fool and she sees through his games. This leads to a power struggle between them that is full of political intrigue and personal drama.
One possible plot could be that Jon Snow finds the Dark Sister in an ancient ruin in the North. He then has to learn to control its power to fight off a horde of undead that are immune to normal weapons.
Well, there's a fanfiction called 'Dark Jon's Ascent'. It shows Jon Snow gradually losing his idealism. He starts to question the traditional values he once held dear after being resurrected. The story delves deep into his psyche as he makes morally ambiguous decisions. Also, 'Jon Snow: The Dark Lord' is quite interesting. It reimagines him as a powerful, yet morally grey figure, ruling over a changed Westeros with an iron fist.