Another possibility is that the fanfiction might focus on the ancestors of the main RWBY characters. Maybe it shows how their families first dealt with the Grimm threat. This would give a different perspective on the RWBY world and the long - standing conflict with the Grimm. It would also allow for a deeper exploration of the lore and history of the RWBY universe in relation to the Grimm.
I'm not entirely sure as it's a fanfiction, but it might feature the main RWBY characters like Ruby, Weiss, Blake, and Yang. Since it's about the Grimm beginning, they could be portrayed in their early days, perhaps just starting to learn about the Grimm and their own powers.
The main character, the child of Grimm, would be at the center. They may have a mentor figure, perhaps an older Huntsman or Huntress who sees potential in them despite their Grimm origin. Then there could be antagonists specific to the fanfiction. Maybe there are those who want to use the child of Grimm for their own evil purposes, like some power - hungry villain in the RWBY world.
Since it's a fanfiction, it could vary a great deal. But likely, it would include some of the main RWBY characters like Ruby, Weiss, Blake, and Yang. Maybe there's a new character who is the so - called 'King of Grimm' that they have to face or interact with.
Since it's a RWBY fanfiction, it might feature the main RWBY team. Ruby Rose, with her silver eyes and scythe - wielding skills, could be a central figure. Weiss Schnee, with her ice - based powers, might also play an important role. Blake Belladonna, the Faunus with her shadow - like abilities, and Yang Xiao Long, the brawler with her gauntlets, could be part of the story too. But it could also introduce new characters created by the fanfiction author that interact with the main RWBY cast during this 'lesson in Grimm brutality'.
Typically, the main characters can still be the RWBY girls - Ruby, Weiss, Blake, and Yang. Since the fanfiction involves Grimm reincarnation, there might also be a central Grimm character that has been reincarnated. It could be a new type of Grimm with unique abilities that the RWBY girls have to face or, in some cases, befriend or ally with.
We might also see other RWBY characters like Weiss, Blake, and Yang. They could be involved in the story to support Ruby or have their own sub - plots related to Ruby's encounter with the Grimm.
Ruby is often a popular character. In RWBY Grimm Gamer fanfiction, she might be portrayed as having an enhanced ability to sense Grimm in the game world. Her speed could also be amped up in a way that makes her especially effective at taking on fast - moving Grimm. For example, she could be the first to reach a new area filled with dangerous Grimm and start clearing them out before the other players arrive.
Yang Xiao Long is a fan - favorite in RWBY Gamer Grimm fanfiction. Her strength and her semblance can be really interesting when combined with the gamer - style storylines. In many of these fanfictions, she might be the one who takes on the tougher Grimm head - on, like a boss - fighter in a game. Additionally, characters like Ozpin can also be important as he might hold the knowledge about the 'gamer' - related mysteries within the RWBY world and the Grimm, guiding the younger characters.
Well, aside from the main RWBY team, it could also have other characters from the RWBY universe as the main focus. For instance, Professor Ozpin might play a major role in a 'a grimm fantasy rwby fanfic'. He has a lot of knowledge about the world and the Grimm, so he could be leading the fight against the Grimm in a more fantastical scenario. Or perhaps Qrow, with his skills and connection to the story, could be a central character. And don't forget about the villains like Cinder Fall. In a fanfic that focuses on the Grimm, she could be teaming up with the Grimm in some new and dangerous way, making her a main character in the story.
Definitely Yang Xiao Long. Her fiery personality and her brawler - like fighting style can create some intense scenes when she crosses paths with the Grimm Reaper. Professor Ozpin is another one. His deep knowledge of the RWBY world and his mysterious past can add layers to a fanfiction involving the Grimm Reaper. Also, Cinder Fall. Her evil plans and her power - hungry nature can make for some great conflict when the Grimm Reaper is in the picture.
Ruby Rose is often a popular character in these fanfictions. Her silver eyes and powerful scythe skills can be combined in interesting ways when considering her as a potential Grimm hybrid. Maybe she could have some Grimm - like abilities that enhance her combat capabilities.