One idea could be exploring a previously uncharted planet full of unique alien species and strange landscapes. The main character could be a scientist on a mission to study these new forms of life.
One idea could be to create an OC who has a Sharingan that has unique abilities. For example, instead of just the normal powers like predicting movements, it could have the ability to see through illusions created by devils in the Highschool DxD universe. The character could be a transfer student, perhaps from a hidden clan that has a connection to both the Naruto world (where Sharingan is from) and the Highschool DxD world. Their backstory could involve some sort of experiment or curse that led to them having the Sharingan.
The male OC could also be a scientist in this fanfiction. He is trying to find a way to end the war between vampires and humans through scientific means. He might be working in a secret laboratory, creating potions or devices that could potentially change the balance of power. He could have a sharp intellect and be a bit of an outcast among his peers.
One idea is to start from the very beginning, like the void before anything existed. Describe how the first element, maybe light or energy, emerged. For example, in some creation stories, there is a powerful being that simply wills light into existence.
For creating a Celestial Wizard OC in Fairy Tail fanfiction, first consider their celestial spirits. They could have unique spirits, like a phoenix spirit for fire - related magic. Also, think about their backstory. Maybe they come from a small village where celestial magic was once shunned. Their personality could be shy yet determined, and their goal in the Fairy Tail guild could be to prove the worth of celestial magic.
Well, for character creation in this RWBY OC with Fairy Tail system fanfiction, you could start with the RWBY aspect. Consider giving your OC a unique weapon, like a scythe that can transform into a ranged weapon, similar to Ruby's Crescent Rose. For the Fairy Tail system, think about what kind of magic your character would have. Maybe they could have ice - make magic like Gray from Fairy Tail, but with a RWBY - style twist, like the ice being infused with Dust. Also, think about their backstory. Were they from Vale and somehow got exposed to the Fairy Tail magic system? This could lead to some interesting plotlines where they have to keep their magic a secret among the RWBY characters or use it to their advantage in battles against Grimm.
Well, for creating an OC (Original Character) as a Dragon God in a Highschool DxD fanfiction, first think about their powers. A Dragon God could have the power of elemental manipulation, like controlling fire or ice. Their appearance could be a mix of human and dragon features. Maybe they have dragon wings that can be hidden at will. Another important aspect is their backstory. They could be an ancient being that has just awakened in the modern Highschool DxD world.
In my opinion, the Starfield story is quite good. It has a unique setting, complex story arcs, and keeps you hooked throughout. The world-building is impressive, and the narrative has depth.