First, decide on the role of the Dragon Grimm OC in the fanfiction. If it's a main antagonist, it should look imposing. It could have multiple heads, each with different abilities. For instance, one head breathes fire, another lightning. Its body can be covered in spikes that are also weapons. If it's a more sympathetic character, give it a softer look, like smaller horns and big, expressive eyes. Its ability could be healing other Grimm, which is very different from the typical destructive abilities of Grimm.
Consider the origin of the OC Dragon Grimm. It could be a result of some ancient magic gone wrong. For its design, add some mechanical - like parts to its body if you want a more steampunk feel. In terms of abilities, it could have the power to teleport short distances. And for its personality, make it more intelligent and cunning. It could use its intelligence to outwit its opponents, especially the Huntsmen and Huntresses in the RWBY universe.
Maybe the OC is a Grimm researcher who is specifically interested in Dragon Grimm. They go on an expedition to find a rare type of Dragon Grimm. Along the way, they encounter a group of Huntsmen and Huntresses who initially suspect the OC of being a threat. But as they face challenges together, they start to trust each other. The OC's knowledge about Dragon Grimm helps them all survive various attacks from other Grimm.
Writers often give them distinct physical features. For example, a humanoid Grimm might have multiple eyes or unusual skin textures. They also give them unique powers, like the ability to control shadows or manipulate ice in a way different from regular Grimm. Their backstories are important too. A humanoid Grimm could have been created from a rare experiment gone wrong.
A half - Grimm OC could fit in as an outcast. Since Grimm are the enemies in the RWBY universe, a half - Grimm would be seen with suspicion. But they could also be a key to understanding the Grimm better. For instance, they might be able to detect hidden Grimm lairs or weaknesses that others can't. They could team up with the main characters like Ruby and the others, gradually earning their trust through their unique skills.
One common theme is the struggle for acceptance. Since the OC is often different due to their Grimm - related aspects, they have to fight to be accepted by the RWBY characters. Another is power and its control. Dealing with Grimm - based powers can be a double - edged sword.
First, consider their origin. They could be from a far - off land where dragon slaying is a common practice, but in the RWBY world, it's unheard of. This gives them an outsider's perspective. Their weapon should be unique too. It could be a combination of a bow and a lance, which they use in different ways depending on the situation with the dragon. In terms of personality, make them a bit of an enigma. They don't reveal much about themselves at first, but as the story progresses, the other characters learn more. For their semblance, it could be something that gives them an edge in dragon battles, like the ability to turn invisible for short periods when they are about to strike a dragon.
Magic could be one way. In the RWBY universe, there could be some form of ancient magic that can change the nature of a Grimm. A character might discover a spell or a magical artifact that has the power to make a Grimm friendly. They would then have to figure out how to use it properly without any negative side effects.
Give your OC a unique goal or motivation. In DxD, there are many power - hungry characters. But your OC could be different. Maybe they want to use their Stand to protect the innocent or to find a way to bridge the gap between different supernatural factions. This will make their actions and decisions in the fanfiction more interesting and distinct from other characters.
Well, there's 'Grimm Origins: An RWBY OC Tale'. This fanfiction dives deep into the backstory of an OC related to the Grimm. It shows how they came to be and their connection to the RWBY universe. Also, 'A Grimm - Bound OC in RWBY' is quite interesting as it explores the challenges an OC with Grimm - like abilities faces in the RWBY world.
One concept could be that the OC is a half - Grimm who struggles with their identity. They might be shunned by both humans and Grimm at first. But as the story progresses, they use their unique abilities, like being able to sense Grimm better than humans and having some Grimm - like strength, to help the RWBY team in their battles. For example, they could be able to sneak into Grimm nests without being detected as easily as a normal human.
Design their appearance based on gaming elements. They could have a hair color that resembles the glow of a game console, or wear clothes with symbols from popular RWBY - themed games. Their weapon could also be something inspired by gaming, like a sword that can transform into a game controller for special attacks.