Perhaps a powerful wizard. Wizards have the ability to use magic, which could be crucial in combating the strange 'ratkness'. They could cast spells to repel the creatures or to discover the source of this 'ratkness'.
It could be a noble knight. Knights in Warhammer are often symbols of heroism and they would be a great fit to lead the fight against the 'ratkness'.
Well, in the context of Warhammer, there are often dark and menacing forces. This 'ratkness' might be a new and unique threat. It could involve battles in different terrains, like the dark alleys of a city or the desolate wastelands. The fanfic might explore how the heroes gather their strength, weapons, and allies to combat this 'ratkness'. They could be facing not just physical threats but also magical or psychological ones.
I'm not quite sure what you mean by 'a light against the ratkness'. Maybe it's some kind of special power or force in the fanfic.
I have no idea who the author of this 'dons adventure lught novel' is. There's not enough information given to determine that.
The main antagonist could be a corrupted figure from the RWBY universe who has allied with some of the darker forces in the Warhammer world. Maybe a character who has been tempted by power and is now using their knowledge of RWBY to help enslave the others. Or it could be a new, made - up character in the fanfic who has a personal vendetta against the RWBY team and uses Warhammer - style enslavement methods.
A psyker might be the main character. Given their connection to the warp, they could sense the power of the Annihilation Maker from afar. They might be drawn to it, either out of curiosity or because they believe they can control it. But they soon find themselves in over their head as the power of the Annihilation Maker is far greater than they expected.
The traitorous Primarchs or their descendants could also be antagonists. If they believe that the awakened Emperor will bring an end to their own power and influence, they would oppose him. For example, the Night Lords' successors might continue their ways of terror and oppose any attempt by the Emperor to bring order.
Akeno could also be a leader. She is powerful and has her own ideas about how the underworld should be. She might be motivated by a desire to change the way devils treat each other and other races. And her relationship with Issei could play a role in gathering support for the coup. She could use her charm and power to sway others to their cause.
Well, it could be a crossover where the dark and gritty elements of Warhammer are introduced into the magical world of Harry Potter. Maybe it's a challenge for the Hogwarts students to face Warhammer - like foes or situations.
It could be Pikachu. Pikachu is a very popular Pokémon and it's not a legendary. It might get tired of seeing the legendaries always in the spotlight and decide to lead the rebellion. Another possibility is Charizard. Charizard is strong and has a bit of a rebellious streak already, so it would make sense for it to be involved in something like this.
Avalanche members could be the main characters. They are already against Shinra's actions in the original story, so it's likely they would be at the forefront of a coup. Barret, with his strong will and leadership skills, could be leading the charge. Tifa, with her combat abilities and loyalty, would be a crucial member. Cloud, with his superhuman strength and his own vendetta against Shinra, would also play a major role.