Team RWBY is definitely crucial. Ruby with her leadership skills and determination, Weiss with her family connections and combat abilities, Blake with her knowledge of the Faunus situation which could be relevant in the post - breach chaos, and Yang with her strength. Ozpin also plays a major role as he has the knowledge and experience to guide the rebuilding process.
In addition to Team RWBY, Qrow Branwen could be a key character. His skills as a huntsman and his connection to Ruby can add a lot to the story. Glynda Goodwitch is also important as she is a powerful figure in Vale. She can be involved in restoring order and training new hunters. Also, the villains like Cinder and her group might still be lurking, so they are important to consider as they could be planning their next move.
Yang Xiao Long could be a key character. Her brash and powerful fighting style might be pitted against the kind of foes from the Man of Steel universe. And Weiss Schnee, with her family's influence and her own ice - based powers, could also be in the spotlight. She might have to use her skills in a different context, perhaps in a more technology - heavy and super - powered environment like in Man of Steel.
One idea could be exploring how the different kingdoms deal with the aftermath of the breach. For example, Vale might focus on rebuilding its defenses and strengthening security. Another could be the character development of Team RWBY. Maybe Ruby becomes more determined to prevent future attacks and starts training even harder. Weiss could use her family's resources to help in the restoration efforts.
Percy Jackson is definitely one of the most important. His leadership during the war and his relationships with other characters make him a central figure. Annabeth Chase too, as she is often the brains behind many plans. Grover would also be important as he has his own unique perspective and abilities that can play a big role in the post - war story.
The protagonist is always a popular choice. You can develop their character further, explore their unspoken thoughts and feelings, and put them in new situations. For instance, in a 'breach of fate' fanfic, the main character might face a moral dilemma that wasn't in the original story.
Luna Lovegood is an interesting choice. She has such a unique perspective on the world, and in the post - war era, she could be involved in exploring the more hidden and strange aspects of the wizarding world that were overlooked during the war. Maybe she discovers new magical creatures or lost spells.
Ruby is always a great choice. In the Mirrorverse, her innocence could be twisted in an interesting way, or she could be the one to bring light to a very dark Mirrorverse. Weiss is also interesting as her family's influence might be different, and she could have a completely different set of skills or abilities. Blake could have a unique story too, perhaps her faunus heritage is more pronounced or has a different meaning in the Mirrorverse.
The members of Team RWBY, like Ruby, Weiss, Blake, and Yang, are also crucial. They are likely to be the ones who will have to deal with the consequences of Torch Wick's return, whether it's fighting against him or trying to understand his motives.
Ruby is always a great choice. Her journey from a young huntress - in - training to a more experienced leader provides a lot of material for fanfiction. You can explore her growth, her relationships with her team, and how she copes with the increasing challenges.
I think Weiss from RWBY could be really interesting to focus on. Her strict upbringing and powerful semblance would contrast well with the more chaotic nature of the Agents of Mayhem. From the Agents of Mayhem, Brick would be a good character. His brute strength and no - nonsense attitude could lead to some humorous and action - packed scenes when paired with the RWBY characters.
Byleth is a very likely candidate. As the main character in the game, their leadership during the war and their influence on the students would likely continue in the post - war period. They could be the one guiding the rebuilding efforts or mediating between different factions. Another is Edelgard. Given her role in the war, she would have a lot to do in terms of making amends and leading her people in a new era of peace. Her character development post - war could be really interesting to explore.