I think you could focus on Hiccup's growth and transformation after the betrayal. Maybe he becomes stronger or learns valuable lessons. Also, you could have him seek revenge or find a way to forgive and reconcile.
First, you should try to understand the underlying emotions causing Hiccup to do that. Maybe he's going through a tough time or facing some internal conflicts. Then, you could explore ways for him to find healthier coping mechanisms, like talking to friends or seeking help from a mentor.
You could have other characters come to his rescue and help him recover.
This is a tricky one. Maybe the other characters could come to Hiccup's aid and help him break free. Or it could be a journey of self-discovery for Hiccup while in that situation.
One way could be to focus on the confusion and adjustments the characters have to make. It can add a lot of drama and humor.
First, you could have the other characters in the story come up with a rescue plan. They might use their skills and knowledge to track down where Hiccup is being held and figure out how to get in safely.
Often, the betrayal could stem from a secret Astrid keeps that accidentally harms Hiccup's interests or trust. Maybe she makes a decision without consulting him that has negative consequences for him.
You could focus on showing his gradual change through significant events or interactions with other characters.
One way is to introduce a special cure or remedy that Hiccup discovers during his adventures. You can also explore how his friends and allies support him through this difficult time.
One way could be to have him go on a solo adventure to prove his worth and find a way back.
It could go a few ways. Maybe the friends of Hiccup form a rescue team and come up with a strategic plan to find and free him. Or, there could be some unexpected twist where Hiccup manages to escape on his own with the help of a dragon. It all depends on the creativity of the author.