A possible plot could be that the baby reader is lost in the strange and often terrifying world that Eyeless Jack inhabits. Jack then takes it upon himself to find a way to return the baby to its proper place or family. Along the way, they form an unexpected bond, with the baby seeing Jack as a protector despite his fearsome appearance.
One interesting plot could be Eyeless Jack protecting the baby reader from other dangerous entities in the fictional world. Maybe the baby has some special power that Jack is drawn to and he feels compelled to keep it safe.
One idea could be that the reader is a new resident in a town known for strange disappearances. Eyeless Jack starts to lurk around the reader's house, leaving small, disturbing signs. Eventually, the reader discovers Jack's lair while exploring an abandoned building. Another could be that the reader is a doctor or nurse, and Eyeless Jack, in his strange way, becomes attracted to the reader's medical knowledge and calmness during dangerous situations.
I'm not really into this kind of 'lemon' fanfiction which often contains inappropriate content. However, generally speaking, in such a fanfiction, it might involve a very specific and often fictional relationship between 'eyeless jack' and the reader. It may explore their interactions in a rather unique and sometimes dark or edgy way, but this kind of content is not suitable for all audiences.
Another idea is that the baby girl is a new creation in Eyeless Jack's realm. She has unique powers that are slowly emerging. As she grows, Eyeless Jack takes on the role of a mentor, guiding her to control her powers and use them for good, or at least for their own survival in that strange and often cruel world.
One popular plot is the reluctant alliance. Ben Drowned and Eyeless Jack might be forced to work together to face a greater evil. Maybe there's a new, more powerful entity that threatens their 'territories' in the horror world.
There's 'A Chance Encounter'. In this fanfiction, the writer does an amazing job of portraying the initial fear of the reader towards Eyeless Jack and then how that fear turns into something more complex like curiosity and eventually a sort of friendship. It's a story that really draws you in with its unique take on their relationship.
One possible theme could be protection. Eyeless Jack might be depicted as protecting the child reader from the horrors of his world. Another theme could be a strange sort of friendship, where the child is not afraid of him and he is intrigued by the child's innocence.
The mystery. Eyeless Jack is a very mysterious character. When paired with the reader in fanfiction, it allows for a lot of exploration of the unknown. Readers are drawn to figure out how the relationship will develop between an ordinary person (the reader) and such a strange and dangerous being.
Eyeless Jack can be developed by showing his softer side when interacting with the baby girl. For example, he might be more patient and gentle, which is a contrast to his usual menacing reputation. This can add depth to his character.
Well, there is a fair amount of jeff x eyeless jack fanfiction out there. In some of these stories, the authors might explore their backstories in relation to each other. Maybe Jeff's actions have some unforeseen impact on Eyeless Jack's existence, or vice versa. These fanfictions can be a great way to see different interpretations of these well - known horror characters.
I'm sorry, but 'eyeless jack x baby' is a very inappropriate and disturbing concept that often involves dark and unethical themes, so I cannot recommend any such fanfiction.