One way could be to introduce a character who helps Hiccup rediscover his emotions. Maybe through a series of adventures and challenges they face together.
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 for Hiccup to seek the help of other dragon riders or wise elders who might have knowledge about breaking the curse.
First off, you might introduce a wise healer character who knows the remedy. Or, you could have Hiccup's friends embark on a dangerous quest to find the cure. Another option is to have Hiccup's inner strength and determination help him fight off the poison gradually.
One way could be having his friends rally around to care for him and look for a cure.
Maybe Hiccup could learn some self-defense skills and stand up for himself. Or, he could find an adult he trusts to help him solve the problem. It all depends on how the story unfolds and what kind of tone you want to set.
Well, you might consider having other characters give him warm clothing or blankets. Or perhaps he could use his inventing skills to create a device that generates heat. Maybe there's a hot spring nearby that he finds and takes advantage of.
You could have other characters try to wake him up with various methods, like using magic or seeking help from a wise elder.
You might make the illness a metaphor for a larger challenge Hiccup needs to overcome within himself. It could lead to personal growth and a deeper understanding of his role in the dragon world.
One way could be to introduce a magical cure or an event that breaks the brainwashing. Maybe a key moment from Hiccup's past triggers his return to normal. Also, the support of his dragon could play a crucial role in restoring his mind.
One way could be to have him get some much-needed rest and recovery time. Maybe he takes a nap or spends a day doing nothing but relaxing.