The story is set in the distant future where almost 2/3rds of the earth is now a wasteland while the rest has been converted into a massive barriered utopia built by the richest and most powerful that is protected by the Sentinels.
Based on this, I imagine the Chimeras are a bunch of villains that have learned to adapt and thrive in the wastes. Each of them have a distinct strength that overcomes an aspect of the wasteland. In fact, I decided to make the story to the point where they have already stolen technology from the Sentinels. This explains why they also have power suits now that enables them to fight equally with the extremely powerful Sentinels.
I named them after demons this time. I guess it fitted their red color scheme as well.
These mutated beings were the work of the exiled members of humanity who believe that the next step in evolution is not just through cyber enhancements but also through forced biological mutations. These beings have adapted to live in underground caves where they have experimented on each other to mutate and evolve to survive the highly toxic atmosphere. They call themselves the Chimeras having mixed their DNAs with various life forms they collected which once roamed the earth. These mutations gave them increased senses and strength. However, their source of energy is limited and extremely difficult to produce due to the difficult terrain and extreme weather on the surface. This forces the Chimeras to constantly attack the city of Corinth and steal whatever energy sources and technology they can to survive and to someday create their own utopia.
I also have a short story for each character which you can read at my post Artstation.
It was really fun to create the images first and then let it inspire my writing next. I don’t think there should be a fixed process to create characters. What matters is you have fun and keep creating!