If I were going to make Malfeas sci-fi, I'd make him an expanding superstructure. A massive tarnished city powered by Dyson Spheres around green suns, with hordes of mechanical demons building it ever outward or repairing the damage caused when solar system-sized sections collapse into each...
I don't have that many problems with mass combat, really. How many fictional bands of ragged freedom fighters have become unstoppable military forces once the main characters decided to get involved?