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.
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 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.
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.
It's possible that she'll form new relationships in hell that will change her. For instance, if she meets a soul who was a victim of her actions on Earth, she could be forced to confront the consequences of her actions directly. This could lead to a transformation in her personality, either towards redemption or further into villainy depending on how she reacts to these new relationships.
Well, a plot could revolve around the father of the baby. He might be in a difficult situation, like being trapped in some sort of supernatural bargain that endangers the pregnancy. Or perhaps the pregnant character forms an unexpected alliance with a former foe because they both have an interest in the well - being of the unborn child. It could add a lot of drama and new dynamics to the fanfiction.
During the pregnancy in the TVD After 8x16 fanfiction, relationships are bound to shift. The mother - to - be's relationship with her doctor, if there is a supernatural - themed doctor in the story, could be one of trust and dependence. Her relationship with other pregnant women in the supernatural community, if there are any, could be a source of support and shared experiences. Also, the relationship between the unborn child's potential godparents and the mother could be redefined as they take on more responsibilities and make promises for the future of the child.
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.
It's the potential for new storylines. In the 'enzo x baby tvd fanfiction', the baby can be a catalyst for all sorts of plot developments. Maybe the baby has some special power, or it could be the key to unlocking a hidden part of Enzo's past. There are so many possibilities to explore, which makes it really exciting for fans to read and write about.