In a fanfiction scenario, Viggo might kidnap Hiccup out of jealousy. Hiccup has a special bond with Toothless, a very rare and powerful dragon. Viggo, who has always been obsessed with dragons, may be envious of Hiccup's connection. He kidnaps Hiccup to try and take Toothless for himself. He might think that by having Hiccup in his control, he can make Toothless obey him. He could also use Hiccup as a bargaining chip to get more dragons from Berk.
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.
One possible plot could be that Toothless is under some sort of spell or mind control. Maybe a new villain in the How to Train Your Dragon universe has the power to manipulate dragons. Toothless, being a powerful Night Fury, is forced to kidnap Hiccup. Hiccup, of course, tries to figure out why Toothless is acting this way and how to break the spell.
One possible plot twist could be that Drago kidnaps Hiccup to use him as a bargaining chip against the dragons. Maybe he wants to force the dragons to submit to his will by threatening Hiccup's life. Another could be that Drago discovers some special power within Hiccup that he wants to harness for his own evil purposes. For example, Hiccup's ability to communicate with dragons might be something Drago wants to use to control all dragons.
Perhaps the ending involves Hiccup actually being the key to saving Toothless from his own actions. Hiccup manages to communicate with Toothless on a deeper level, and they work together to defeat the real enemy that was causing Toothless to act out. In the end, their bond is stronger than ever, and they continue to protect Berk side by side.
First, you need to have a clear idea of their characters and the setting. Then, think of an interesting plot that could involve both Hiccup and Viggo. Maybe start with a conflict or a mystery for them to solve together.
Well, it varies a lot in fanfiction. Sometimes Hiccup and Viggo become unlikely friends, while in others, they remain bitter enemies. The plot depends on the author's imagination and creativity.
You might have the dragons play a crucial role. They could sense Hiccup's distress and lead the others to where he is. Or, there could be a secret weapon or magic that the heroes discover to defeat Viggo and free Hiccup.
One possibility is that Artemis has been misinformed. Some enemy of Percy has tricked her into thinking that Percy is a danger to the demigods. So she kidnaps him to stop him from causing harm. But as she keeps Percy captive, she slowly realizes that she has been deceived when Percy starts to explain his side of the story and the real threats he has been fighting against.
The plot could involve the Phantom seeing Christine as his only salvation from his lonely and tortured existence. So, he kidnaps her with the intention of making her understand his world. He may show her his musical creations, hoping she'll come to love him in return. However, Christine might be initially terrified and try to escape.
In some fanfictions, Aizawa might be under the influence of a villain's quirk that makes him act against his will. So, he kidnaps Izuku, but later on, he realizes what he's done and tries to make amends. This could lead to a story full of drama and redemption.