It could be an estranged family member with a grudge. Perhaps a relative who feels wronged by Marco's family and decides to take revenge by kidnapping Marco. Or it could be a deranged fan who has an unhealthy obsession with Marco and wants to keep him all to himself.
Some stories might have the theme of unexpected alliances. For example, Marco could form an alliance with another captive or even with one of the kidnapper's minions who has a change of heart. There's also the theme of self - discovery. Through the harrowing experience of being kidnapped, Marco might learn things about himself that he didn't know before, such as his inner strength and resourcefulness.
The themes could also include redemption. After kidnapping Marco, Tom might realize the error of his ways and try to make amends. And there could be a theme of friendship. Even though Tom has kidnapped Marco, the story could explore if their friendship can be salvaged.
I'm not sure specifically which 'tom kidnaps marco fanfiction' you are referring to. There could be many different interpretations and stories with such a premise in the fanfiction world. It might involve a complex plot where Tom, for some reason, decides to kidnap Marco. Maybe it's due to jealousy, or a misunderstanding in their relationship within the context of the original story it's based on.
Well, first of all, it would be a very dark turn for the characters. Amy would likely be terrified, and Sonic would be seen as a villain, which is completely against his heroic nature in the main series. It could also make the readers uncomfortable as it involves non - consensual actions.
It could be a rogue vampire who wants Bella for her unique blood. There are many vampires in the Twilight world who might be tempted by her smell. Another potential kidnapper could be a vengeful werewolf who blames Bella for something, perhaps for the way the vampires and werewolves' relationship has changed. It might also be a human who has somehow found out about the vampire world and thinks they can use Bella to gain power or knowledge.
The Sith could be potential kidnappers. They might see Princess Leia as a powerful Force - user and want to either turn her to the dark side or use her in some dark ritual. Another possibility is the bounty hunters. They could be hired by some powerful and shadowy figure to kidnap Leia for various reasons, like for political leverage or to get information from her. Also, a new and unknown alien race that has just entered the galactic scene could be the kidnappers. They might not understand the significance of Leia but kidnap her out of curiosity or because they misinterpret her actions as a threat.
It could be a group of rogue demigods who are jealous of Percy's status and power. They might think that by kidnapping and torturing him, they can gain some of his abilities or just to prove that they are stronger.
It could be a group of rogue Death Eaters who want to use baby Harry as a bargaining chip against Voldemort. They might think that by having Harry, they can gain power within the dark wizard's ranks or even overthrow him.
The potential kidnappers could be a secret society within the wizarding world that has its own agenda. They might believe that Hermione has a special power or connection that could either help or harm their cause, so they took her at birth to control that. It could also be a non - human magical being, like a centaur or a goblin, who thought that Hermione's birth was a sign of something significant in the magical world. They kidnapped her to study her or use her in their own cultural or magical practices. Or perhaps it was a wizard who had a grudge against Hermione's parents and took their child as revenge.
Hermione could be a potential savior. She's smart and resourceful. She might figure out where Lockhart has taken Harry by using her vast knowledge of magic and Hogwarts' secrets.