A dragon with a unique ability, like the power to manipulate time. This dragon could be an antagonist at first, but as the story progresses, it could become an ally or at least a complex character with its own motives that are not entirely evil. It would add a lot of mystery and intrigue to the fanfiction.
An old wizard who has knowledge about titanium dragons and their slayers. He could act as a mentor to the slayer, providing crucial information and spells when needed. His backstory could be intertwined with the history of dragon slaying, and his presence could add a sense of wisdom and depth to the story.
A young apprentice who looks up to the titanium dragon slayer could be a great character. They could be full of enthusiasm and naivete, constantly asking questions and getting into trouble, but also providing a fresh perspective on the world of dragon slaying.
The titanium dragon slayer could be cursed. Every time they attempt to slay a dragon, they are instead inflicted with a part of the dragon's power, slowly turning them into a half - dragon, half - slayer hybrid. This transformation makes them an outcast among their own kind and forces them to reevaluate their role in the world of dragon slaying.
Lucy would be a great character to include. She could help Natsu research about water dragon slayer magic. Gray could also be there, and they could have some friendly rivalries regarding the different elements. Happy would be essential as Natsu's sidekick, providing comedic relief and also helping in some tricky situations.
There could be a wise old mentor who was also a poison dragon slayer in the past. He can guide the main slayer with his years of experience and knowledge about different poisons and dragons.
It's possible that there's a love interest for Percy in the fanfiction. This character could be another adventurer or someone from Percy's past. Their relationship could add an emotional aspect to the story, as Percy has to balance his feelings for this person with his dangerous job as a dragon slayer.
In some fanfictions, Happy, the flying cat, could also be an important character. He could provide comic relief and also be involved in some of Lucy's adventures as a dragon slayer. For example, he might help her find clues or get out of difficult situations. And then there could be original characters created specifically for the fanfiction. These characters could be other dragon slayers or powerful mages that interact with Lucy in different ways.
Since I don't have the actual fanfiction, it's hard to say for sure. But it's likely that the dragon slayer is a main character. There could also be other characters like villagers who are being affected by the situation related to 'the nothing' and perhaps other dragon slayers or mentors.
Typically, the main character is the dragon slayer. They are often a brave and determined individual with unique skills and a strong will.
One of the main characters could be Happy, Natsu's loyal flying cat companion. Happy would likely be by Natsu's side during his retirement, still providing his comical relief and support. Another character could be Lucy. She might be concerned about Natsu's retirement decision and try to understand his reasons, or she could also be retiring from her own magical adventures and join Natsu in his new peaceful life.
Perhaps a young and inexperienced adventurer who discovers their hidden power while on the quest to slay the dark dragon. They grow throughout the story, learning new skills and becoming a true hero.
A powerful dragon - themed pirate could be the main antagonist. This pirate has a crew of dragon - like creatures and they are causing chaos across the seas. They have a grudge against Luffy for some reason, perhaps because Luffy has unknowingly entered their territory or stolen something valuable from them.