An OC could be a lost traveler from another region. They have different technology and knowledge compared to the people in the Dramatical Murder world. This causes both curiosity and suspicion among the existing characters. The OC's journey could be about trying to find their way back home while getting involved in the local politics and power struggles, and ultimately having to choose between going back or staying to help their new friends.
One common theme is self - discovery. The characters in the original work are complex, and in fanfiction, they often go on journeys to understand themselves better. Another theme is relationships, like the development of friendships or romances among the characters.
First, study the existing characters in Dramatical Murder. Notice their traits, like their strengths, weaknesses, and personalities. Then, for your OC, give them a backstory that fits within the world. For example, if they are from the same area as the game characters, what events in their past made them who they are? Also, give them unique skills or flaws. Maybe your OC is really good at fixing old machinery but is terrible at communicating with others. This makes them more real.
Another plot could revolve around an OC who is a Spartan trainee that doesn't quite fit the mold. They have a different way of thinking and approaching combat. In Halo 4, they end up being the key to solving a mystery related to the Prometheans. Maybe they find a way to communicate with the Prometheans and convince some of them to stop fighting the humans.
One idea could be an Otsutsuki OC who comes to Earth not for conquest but to study the unique life forms here. They could befriend some of the local ninjas and learn about the concept of friendship, which is alien to the Otsutsuki. This would lead to a series of adventures where they have to protect their new friends from other more hostile Otsutsuki members.
One idea could be an OC who is a long - lost relative of Moana. This OC could have been separated from the family during a great storm years ago. They could have unique skills, like being able to communicate with a different type of sea creature that Moana has never encountered. This would bring new adventures as Moana and the OC try to figure out how this new discovery could help their island.
One idea could be exploring the origin of the OC in the covenant world. Maybe they have a special power that sets them apart from the regular covenant members.
One idea could be an OC who is a new Wolfblood in a pack and has to prove themselves. Maybe they have a unique power that the others don't have and they have to learn how to control it while fitting into the pack's hierarchy.
One idea could be an OC who is a long - lost relative of one of the main characters. They suddenly show up and cause a stir in the power dynamics. For example, if they are related to the main heir, they might have a claim to the inheritance as well, leading to all kinds of family drama and power struggles.
One idea could be an OC who is a brilliant but unorthodox medical student. They constantly clash with House in their diagnostic methods yet prove to be surprisingly accurate at times. For example, they might use a new technology or approach that House is initially skeptical about but later comes to respect.
One idea could be an OC with the power to manipulate time joining the Incredibles. They could use their power to prevent disasters or even go back in time to change events that led to Syndrome's rise. Another idea is an OC who is a super - fast healer. They could play a crucial role in patching up the Incredibles after tough battles.