The princess is the key character, and often a noble knight with a chivalrous code is present. There could be a group of bandits who initially seem like they are part of the kidnapping but later turn out to be helpful. Another character could be the princess's father, the king, who is desperate to get his daughter back and may take extreme measures. There might also be a mysterious figure, like a hermit with great knowledge, who gives the rescuer some crucial advice or a magical item to help in the rescue.
The princess herself is of course a main character. Then there's often a dashing prince or a heroic knight as the rescuer. Sometimes a wizard or a sorceress can be involved, either helping the captors or coming to the princess's aid. And there may be a villain like an evil lord or a dark sorcerer who is behind the kidnapping.
Definitely the princess is a central figure. A brave rogue or a mercenary who is hired to rescue the princess can also be a popular character. In some fanfictions, the princess's loyal maid or servant who tries to find help for her mistress is also seen. And not to forget, the kidnapper who could be a power - hungry warlord or a mad scientist in some more unique takes on the genre.
Villains also often show up. For instance, the Joker from Batman. His chaotic nature can be used to create some really edgy and interesting rap lines. And then there are characters from classic literature like Sherlock Holmes. His intelligence and deductive skills can be turned into cool rhymes in the rap battles.
There could be a mentor - like figure in the kidnapped bride fanfiction. Maybe an old wise woman who gives the bride advice on how to deal with her captor or escape. This character can play an important role in the bride's journey and is often quite popular among readers for their wisdom and guidance.
Often, you'll see brave warriors as main characters. They are the ones who take on the Darkness head - on.
Typically, you'll find a protagonist who is either directly affected by the divine darkness or has a personal vendetta against it. For example, a character whose family was destroyed by the darkness. Additionally, there could be a group of side characters like a band of adventurers who join the fight. There may also be a villainous character who wants to harness the power of the divine darkness for their own evil purposes.
Often, there is a young and brave female protagonist. She is usually curious and has a strong will. For instance, she might be a girl who was born in the cloud world and is eager to explore beyond the familiar clouds she grew up around.
Often, the vampire leader is a popular character. He's usually depicted as strong, mysterious and with a certain charm. The kidnapped character themselves can also be really popular as readers follow their journey of survival and adaptation in the vampire world.
Dragons are obviously the main characters. There are different types like the powerful red dragons known for their fire - breathing abilities. Then there are the more mysterious black dragons.
Space Marines can also be main characters. They might be tasked with protecting an STC site or escorting Tech - Priests to retrieve an STC. Their combat skills are crucial in fending off threats.
Often, Colonel Miles Quaritch is a main character. In the fanfiction where humans win, he might be portrayed as a more heroic figure, leading the human troops to victory with his military expertise. Another character could be some brilliant scientist who discovers the key to human success on Pandora. And of course, there could be new characters created by the fanfic writers, like a human - Na'vi hybrid who sides with the humans and uses their unique abilities to help the human cause.
Often, Naruto himself might be a main character in such fanfiction. He could be given the blue Sharingan through some strange event and then has to learn to use it. Another common character could be Sasuke. He might be involved in a plot where he discovers someone else with the blue Sharingan and either tries to help them or sees them as a threat.