In the fanfiction, perhaps there's a moment when Hiccup gets injured while protecting the village. Astrid stays by his side day and night, taking care of him. She reads to him, makes him his favorite food, and in those quiet days, they realize how much they mean to each other. Their love deepens as they share these tender moments.
Well, Hiccup is very resourceful. He could use the environment around him to his advantage. If he is locked in a place, he might find a weak spot in the structure, like a loose board or a hole in the wall. And he could call for Toothless secretly. Toothless, being highly intelligent, could find Hiccup and rescue him. Also, Hiccup could befriend some of Viggo's minions and convince them to help him escape.
Toothless is the most likely one. Their bond is so strong that Toothless would sense Hiccup's distress and come to his rescue. He could fly into Drago's hideout and cause chaos to free Hiccup.
The setting is important too. It could be the familiar Berk or some new, uncharted lands. A different setting can bring new challenges and opportunities for Hiccup. For instance, if it's in a land filled with ice and snow, Hiccup has to deal with the harsh environment as well as any threats that might lurk there. Also, the other characters from the original story, like Astrid or Stoick, might play different roles in the fanfic, either supporting Hiccup or creating conflicts for him.
I'm not entirely sure specifically what 'hiccup black fanfiction' is about without reading it. But generally, in fanfiction, when something is 'black', it could imply a darker take on the source material. So for Hiccup, it might be about him facing moral dilemmas, being involved in a darker plotline like in a world full of chaos or corruption, and how he navigates through it in this fan - created version.
There could be a young girl from a far - off land who has a special bond with a rare type of dragon. She and Hiccup could join forces. She might have unique skills like being able to communicate with dragons without words. And also, an old hermit who has been living alone with his dragon for years. He has a lot of wisdom about the ancient ways of dragon riding and could help Hiccup on his travels.
There could be Toothless. Even though Hiccup is now a dragon, his connection with Toothless from his previous human life might still be there. Toothless could play a crucial role in helping Hiccup adapt to his new form.