I find that having Malfeas be nice and huge has two very good effects:
1: It allows me to ignore most of it. I mean, there are a lot of Yozi and demons and so on. Not even getting into first circles, we have 23 Yozi, at least an order of magnitude more Third Circle demons, seven times that number of Second Circles, a large number of Behemoths and other horrors and monstrosities sealed away at the end of the Primordial War. Given the scale these beings operate at, it’s fairly easy for me to do stuff like have all my plot happening way over there away from any NPCs I don’t want to deal with. I can have all sorts of hidden stuff in there, entire societies that exist isolated from the rest of Malfeas and that nobody has ever heard of. Vast tracts to explore.
2: It touches on the ultimate futility of trying to conquer/destroy it. Octavian is noted for his feat of managing to conquer one quarter of one layer of Malfeas and he’s supposed to be one of the setting’s big badasses. Hell is this giant messy, horrible place full of slaves and abusers and you are such a tiny part of it, even as a mighty Solar. How can you hope to fix this massive thing? This plays into my favorite interpretation of Malfeas… you shouldn’t use it as a evil empire, you should use it as Fantasy Iraq, a subaltern nation broken and subjugated by Creation, full of all sorts of horrible infighting and atrocities of all types, which Creation milks for valuable resources and which occasionally inflicts ultimately useless acts of terrorism on Creation.