Perhaps the dragon is guarding something in the tower. Lucy could find a way to communicate with it and convince it to let her have whatever it's guarding. For example, it could be a magical item that has the power to break the tower's spell or open a portal to another world. She might start by offering the dragon some food she has with her or by using her knowledge of ancient languages to talk to it. If she can gain the dragon's trust, they could work together towards a common goal.
Well, in this fanfiction, Lucy might initially be scared when she meets the dragon. Maybe the dragon is a huge and fearsome creature with scales that shine in the sunlight. She could try to run away at first.
In fanfiction, the tower could have some sort of magical protection or power that Lucy can use to her advantage against the dragon. Maybe there are magical symbols on the walls that she can activate to create a shield around herself. Or perhaps there is a special room that the dragon cannot enter. She can retreat to this room when she feels threatened. She could also try to tame the dragon over time. By showing kindness and not being a threat herself, the dragon may gradually become more friendly towards her and she can then survive more easily in the tower with it.
It's possible that in this fanfiction, Lucy and Acnologia meet in a neutral territory. Lucy, with her kind heart, tries to communicate with Acnologia. Acnologia, who has been alone for a long time, is initially hostile. But as Lucy persists, she manages to break through his tough exterior. They might then share stories about their pasts, with Lucy talking about her guild and Acnologia about his past as a dragon.
Well, for starters, Gru would probably be very protective of Lucy. He's not one to show a lot of softness usually, but with his wife being pregnant, he'd be different. He might start to cut back on some of their more dangerous adventures.
Well, she might meet historical figures. For example, she could encounter Cleopatra and have an interesting conversation about ancient Egyptian politics and culture.
She might lose her friends. In the original story, her friends in Fairy Tail are a big part of her life. If she joins a dark guild, they would likely see her as a traitor. For example, Natsu might be very disappointed and try to bring her back to the right side.
Well, there could be a lot of chaos at first. Maybe they'd argue over who gets the best rooms. Tony might want to keep all the high - tech rooms for himself. And Thor could be constantly breaking things because he's not used to Earth technology.
It could be about Lucy having an adventure in the world where celestial dragons exist. Maybe she befriends one or tries to change their cruel ways.
One thing that could happen is that Gru would become more cautious. He has a dangerous job sometimes, and with Lucy pregnant, he might not take as many risks. He'd want to be there for her and the baby.
Midnight might use his illusions to make Lucy think she's lost her Celestial Keys. This would be a huge psychological blow to her. But then Lucy could remember the bond she has with her spirits and break through the illusions. It would be a battle of wills as much as magic.