I'm guessing the "proper gods" are the final enemies that turn out to be the ones actually manipulating humanity and stuff behind the scenes, maybe to cultivate faith/soul farms or whatever...
Actually, thinking further about the "exterior" realm or wherever that is the outer gods from... Maybe the humanity are like cultured fungi in a lab (mortal realm) that produce antibiotics (faith/souls/whatever) that the scientists (proper gods) manage them for... Outer gods could be ascended humans/demons, which Karna (and the fox demon lord) may be become eventually, and reach "exterior" with his revived outer gods party to fight the proper gods. Probably there will be civil wars among humans too splitting them into proper gods faction (which would include the religious people and heroes) and others (like assassin girl etc) after the truth about the outer gods vs proper gods, demons vs humans is revealed.