Well, you could have an OC that is a dragon - shapeshifter. In the fanfiction, this character has to hide their true identity in a world where dragons are feared. They might fall in love with a human who initially hates dragons but then discovers the OC's secret. Or, consider an OC that is a fairy with the power to manipulate time, but using this power has dangerous consequences.
A cool concept for Mythical Creatures OC Fanfiction would be an OC that is a werewolf - vampire hybrid. This OC would be constantly struggling with the conflicting natures of both species. They could be part of a secret society that tries to keep the peace between werewolves and vampires. You could also write about an OC that is a griffin - tamer. This OC has a special bond with griffins and goes on adventures with them to protect their nesting grounds.
One idea could be to create a fanfiction about a half - human, half - phoenix OC. The OC could be on a quest to find a way to control their phoenix powers which keep flaring up at inopportune times. Another idea is an OC that is a mermaid - centaur hybrid, living in a hidden underwater - forest realm.
One idea could be creating an OC who is a half - human, half - caster. This OC could struggle with fitting into either world and have a unique journey of self - discovery. For example, they might be shunned by both humans and casters at first but gradually find their own place. Another idea is an OC with a special power that no other caster has, like the ability to control time in a limited way. They could use this power to change the course of events in the Beautiful Creatures universe, but also face the consequences of messing with time.
One idea could be a story where a powerful mythical creature is awakened in Fiore and the Fairy Tail guild has to figure out how to calm it without using brute force. Maybe it was awakened by dark magic accidentally.
For a Harry Potter magical creatures fanfiction, you might consider writing about hippogriffs. Maybe a story where a character is wrongly accused of mistreating a hippogriff and has to prove their innocence. Or perhaps a fanfic that dives into the breeding habits of magical creatures, specifically centaurs. Explore how they raise their young and the unique magic involved in their family structure.
One interesting aspect in 'Harry Potter breeding creatures fanfiction' is the breeding of Thestrals. Some fanfictions might explore breeding Thestrals with a better understanding of human emotions so that they can be more effectively used for transportation. There could also be stories about breeding Nifflers to be more intelligent, able to detect not just shiny objects but also objects with a certain magical signature. This could lead to new adventures where the characters use these enhanced Nifflers to find lost magical artifacts.
One idea could be a story about a young wizard who discovers a new, rare magical creature in the Forbidden Forest and tries to protect it from dark wizards who want to use its powers for evil. Another could be a fanfic where a group of Hogwarts students form a club dedicated to studying and caring for magical creatures, and they encounter various challenges and adventures along the way. A third idea is a story that focuses on the relationship between a magical creature and a character who has the ability to communicate with it telepathically, and how they work together to solve a mystery at Hogwarts.
One way to make your Mythical Creatures OC Fanfiction stand out is through complex relationships. If your OC is a siren, have it form an unlikely friendship with a mermaid who is usually an enemy in traditional lore. Another aspect is the plot. Instead of a simple 'good vs evil' plot, create a multi - layered plot where different factions of mythical creatures are vying for power and your OC is caught in the middle. Also, use a unique writing style, like writing from the perspective of the mythical creature itself, which can give readers a fresh experience.
One idea could be creating an OC who has a unique power related to time manipulation. They could be from a different dimension and end up in the Avengers' world. Another idea is an OC who is a master of ancient magic and teams up with Doctor Strange within the Avengers group. Maybe an OC that is a super - intelligent android created by a villain but has a change of heart and joins the Avengers.
You could create an OC for your Persona OC fanfiction who is an artist. This artist OC could use their art as a way to understand and even manipulate the Metaverse. For example, they might draw scenes from the Metaverse that give clues about upcoming events or hidden locations. Their art could also be a form of therapy for other characters who are struggling with their dual lives in the real world and the Metaverse.
Perhaps an OC who is a half - human, half - beast creature. This OC could struggle with acceptance in both the human and beast - kin societies. They end up meeting the main characters during their adventures and learn to embrace their unique identity with the help of the group, while also adding their own combat skills, which are a blend of human strategy and beast - like strength, to the team.
One idea could be to explore the Riddler's origin story from the perspective of your original character (OC). Maybe your OC is a detective trying to solve the mystery of the Riddler's first crime spree. Another idea is to have your OC be a sidekick of the Riddler, either willingly or by being forced into it. They could then have a complex relationship where the OC tries to influence the Riddler's actions for better or worse.