An old wizard who has knowledge of time magic. He could be a mentor figure for the other characters trying to stop the thief of time. He has his own secrets and a past connection to the time - stealing phenomenon, which could be revealed as the story progresses.
A young hero who discovers the existence of the time thief and decides to stop them. This character could start out as an ordinary person but grow and develop special skills and knowledge as they battle the thief.
It could be the thief of time themselves. We could get to know their motives, their daily life of stealing time, and their inner thoughts. It would be a very unique perspective.
It could be a new character, like a street - smart orphan who has learned to steal to survive. This character sees Fairy Tail as a source of wealth at first but then discovers there's more to the guild than just gold and jewels. Another option is an ex - member of a rival guild who turns to thievery after being exiled and decides to target Fairy Tail for revenge. Or it could be a magical creature, like a mischievous imp with the power of invisibility that steals from Fairy Tail just for fun.
The main character would most likely be the new thief. They could be an original character created just for this fanfiction.
A new character who is a skilled acrobat could be a great thief. They could use their acrobatic skills to easily get in and out of places unnoticed. Their backstory could be that they grew up in the circus and had to turn to thievery due to some misfortune.
I don't know who the main character is since I haven't read the book. But it's probably the time thief. After all, the title mentions a 'time thief' and the story is likely centered around this character.
In the Harry Potter fanfiction, the 'thief of time' could be a character that has been overlooked or underestimated. It could be a young wizard who discovers a powerful but dangerous magic related to time. He might not fully understand the consequences of his actions and accidentally becomes the 'thief of time'. Or it could be a shape - shifter who uses different forms to steal time without being detected easily. They could be stealing time from important magical ceremonies or from the lives of key characters in the story.
An unknown wizard from a far - off land could be a thief in Harry Potter fanfiction. This wizard could come to Hogwarts or the wizarding world of Britain with the intention of stealing unique magical items that are not found in their own land. They would bring a sense of mystery and a new cultural perspective to the story.
Perhaps the thief is a corrupted official in the Yugioh tournament world. He uses his position to steal valuable cards from the best duelists at night. He believes that by having these cards, he can control the outcome of important tournaments and make a lot of money through illegal gambling on the duels. But his actions start to draw the attention of some of the more ethical characters in the Yugioh universe, and they begin to investigate.
Definitely Percy Jackson from 'The Lightning Thief' and Iron Man from the Avengers would be main characters. Iron Man with his high - tech gadgets and Percy with his demigod powers would make for an interesting duo. They could play off each other's strengths and weaknesses. Maybe Iron Man is constantly trying to analyze Percy's powers with his technology while Percy is just like 'Let's just go and fight already!'
A new character created specifically for the fanfiction could be the main character. This character could be an underdog, not as strong as the well - known fighters. But in the hyperbolic time chamber, they discover their hidden potential and strive to prove themselves against the more established heroes.
Izuku Midoriya would be a great choice. His determination and analytical mind would make it interesting to see how he deals with a time loop. He could use his knowledge from each loop to better himself and his classmates.