One possible plot twist could be that Pitch kidnaps Elsa not for his own gain directly, but to use her as a bargaining chip with the other guardians. For example, he might demand that the guardians give up their powers in exchange for Elsa's safe return. Another twist could be that Elsa discovers a new power within herself while being held captive by Pitch. Maybe her fear and the dark environment somehow unlock a power that is related to shadow or ice in a new way. And a third idea is that Pitch kidnaps Elsa because he realizes that her powers are a key to unlocking a greater power source that he wants to control, but Elsa manages to resist his attempts to use her in that way.
Well, Anna would be frantic. She'd immediately set out to find Elsa, not caring about the danger. She might even team up with the Guardians without hesitation. Kristoff would be right by Anna's side, using his survival skills to try and track down Pitch's location. Olaf, being the innocent and loving character he is, would be heartbroken. He might try to cheer Elsa up from afar by singing or reminiscing about their good times, hoping it reached her somehow. The trolls, if they found out, would offer their wisdom and perhaps some magical aid to help in the rescue of Elsa from Pitch's clutches.
Anna could be the one to save Elsa. After all, she has proven herself brave and determined in the original story. She would stop at nothing to rescue her sister from Hans's clutches.
One common theme is the power struggle. Since both Elsa and Pitch have strong and distinct powers, many fanfictions explore how they deal with each other's powers. For example, Elsa's ice powers might be a counter to Pitch's nightmares or vice versa.
Another theme is the idea of isolation. Elsa has been isolated because of her powers, and Pitch is often seen as an outcast in the world of good. Fanfictions may explore how they deal with their loneliness and whether they can find understanding in each other.
There might be. Fanfiction writers can come up with all sorts of creative and unexpected pairings. However, it's also possible that this particular pairing is not very common. It depends on how popular the idea of Elsa from 'Frozen' and Pitch Black from 'Rise of the Guardians' crossing over in such a romantic way is among the fanfiction writing community. You may need to dig deep into different fanfiction categories and tags to find it.
One possible plot in this fanfiction is that Hans kidnaps Elsa not just for power or revenge, but because he is being controlled by some dark magic. He takes Elsa to a remote location where she has to fight not only Hans but also the source of the dark magic to free herself and save Arendelle. Along the way, Elsa might discover new aspects of her powers that she didn't know before.
Jack could use his ice powers to create a distraction. For example, he could make a large ice structure that startles Pitch and gives Jack a chance to run. Another way is if he can find Pitch's weakness. Maybe Pitch is afraid of a certain light or sound, and Jack can use that to his advantage to escape.
Well, in many 'Elsa x Pitch Black' fanfictions, the theme of transformation is quite common. Elsa might transform Pitch Black's view of the world, and he might in turn help her embrace a different side of herself. There's also the theme of the outcast. Both characters have elements of being outcasts in their original stories, and in the fanfiction, they might find solace in each other's company, creating a bond based on that shared experience.
Yes, there are some out there. You can start by looking on fanfiction websites like Archive of Our Own. Just search for 'Elsa x Pitch Black' and you'll find a variety of stories with different takes on their relationship, from angsty to fluffy.