Create a backstory that ties into their Changeling nature. Maybe they were an outcast in their Changeling community because they refused to use their abilities for bad deeds. This backstory can influence their actions and decisions in the fanfiction. They could be more determined to prove themselves good in the Fairy Tail world.
You can give your Changeling character unique physical traits even when they change forms. For example, they might have a distinctive eye color that remains the same no matter what form they take.
You can start by changing their backstories. For example, if you want to make a unique Lucy, instead of being from a rich family, she could be an orphan raised by street mages. This would change her personality and how she approaches magic. She might be more street - smart and less naive.
For Earthland characters, you can draw inspiration from different cultures and mythologies on our own Earth. For example, if you want to create a mage with water - based magic, you could base their appearance and personality on the mermaids or water spirits from various folklore. In Edolas, since it has a different magic system, you could create characters whose powers are related to the technology - like magic there. Maybe a character who can manipulate the magical energy in machines.
You could give a character the power to manipulate the drinks in the bar. For instance, they can make a cocktail that gives temporary super strength or the ability to see through illusions. Just think of how that would interact with the other characters and the story.
You can start by combining the traits of different Celestial Spirits. For example, take the loyalty of one spirit and the mischievousness of another to create a new and interesting character.
You can combine the characteristics of robots and the magic from Fairy Tail. For example, a robot character could have a magic core that gives it special powers. It might be able to transform into different forms depending on the type of magic it absorbs. Another way is to give the robot a personality based on its function. If it was designed as a healer - type robot, it could be very gentle and nurturing.
First, consider their magic. For a Wizard Saint, it should be something very powerful and perhaps a bit rare in the Fairy Tail world. It could be a combination of different types of magic, like a blend of fire and time magic.
You can give them unusual magic powers. For example, the power to control shadows in a very distinct way, like creating living shadow creatures. Also, give them a unique backstory. Maybe they were raised by a group of magical beasts instead of humans. This would make their perspective and behavior different from the regular Fairy Tail characters.
You can start by mixing the traits of existing characters. For example, take the determination of one character and combine it with the playfulness of another. This can create a new and interesting personality.
To create a unique Fairy Tail Guardian OC, consider their personality traits. Instead of the typical brave and hot - headed like some of the Fairy Tail characters, your OC could be more calm and calculating. They analyze situations before acting. For their magic, it could be related to emotions. For instance, they can absorb the negative emotions of others and turn them into a powerful blast of energy. In terms of their look, they might have a tattoo on their face that glows when they use their magic, which is a sign of their guardian status.
Base their powers on something unique. It could be related to their emotions, like a character whose magic gets stronger when they're angry. Or it could be tied to an object they carry, such as a necklace that gives them the ability to control water. Their powers should also have limitations, which can add to the drama and conflict in the story. For example, if a character can fly, but only for a short period of time before getting exhausted.