Another plotline might involve Katherine encountering supernatural entities in hell that she has to deal with. These entities could either be there to torment her further or they could offer her a chance at redemption, which she would have to struggle with as her character is known for her self - serving nature.
Perhaps it could explore her past actions in more detail while she's in hell, like how her wrongdoings on earth are now being punished or how she reflects on her relationships, especially with Stefan and Damon. It could also show her facing her inner demons, both literally and figuratively, as she tries to find a way out of the hellish realm.
Obviously, Katherine herself. Also, there could be appearances from demons or other hellish creatures that are part of the hell setting. Given her history, Stefan or Damon might make appearances in her memories or even in some sort of spectral form if the fanfiction has elements of the afterlife being connected to the living world.
One possible plot could be Katherine coming back from hell with new powers. Maybe she seeks revenge on those who wronged her before. She could target Elena specifically, creating a lot of chaos in Mystic Falls.
One possible plotline could be about Enzo protecting his daughter from the various threats in the TVD universe. Maybe she has a special power that makes her a target, and Enzo uses his vampire skills to keep her safe.
Perhaps she forms an unlikely alliance with other damned souls in hell. They might work together to try and find a way to escape or at least improve their situation in hell. It could involve some sort of power struggle among different groups of souls in the hellish realm.
Obviously, Katherine would be one of the main characters as the story is centered around her time in hell and what happens after. Damon and Stefan would also be important as they have a long history with Katherine. Their reactions to her return would be crucial to the plot.
One possible plotline could be that Harry discovers his true heritage as a prince of hell and has to grapple with the dark powers that come with it while still trying to exist in the wizarding world. Another could be that he is in conflict with the forces of good in the wizarding world as they view his newfound identity as a threat. Maybe he has to form new alliances with darker creatures or beings from the underworld.
One possible plotline could be the exploration of new and powerful cards that emerge from a rift in time. These cards might have unique abilities that disrupt the existing dueling order in the Yugioh universe.
One possible plotline could be Lionel Alistair starting as a young and ambitious character. As time passes, he faces various challenges in his career. For example, he might have to compete with a rival who is constantly trying to undermine him. Along the way, he also falls in love with a kind - hearted person who supports him through all his difficulties. This love story intertwined with his professional struggles could make for an interesting fanfiction.
One possible plotline could be Drizella's journey to find true love. Maybe she starts off as a rather unlikable character, but through a series of events, she meets someone who sees the good in her. They go on adventures together, and Drizella slowly changes for the better, learning about kindness and self - sacrifice.
One possible plotline could be that Emma gets injured during a heroic act. Maybe she was trying to save a friend or protect her community from some sort of danger. Her injury then becomes a turning point in the story, leading to her having to rely on others for help while she recovers. This could also lead to some self - discovery and new relationships forming as she is forced to be more vulnerable.