In the Harley there is a moment in the First World where we see a number of haloed people going down to extract what can only be "forbidden sun" or what we tentatively call the perfected/complete Mother Flame.
Whatever that sun did is out of the question now, though it is wholly distinct from the Sun God, Nika.
What I want to ask around about though is that now that we have two "gods" sharing the signature halo, Imu and Zaza, what do you think is most likely to be true?
• a god or multiple gods bestowed halos, like Imu's Omen for the people extracting the forbidden sun?
• a halo was a signature mark of the old world's power system and what made these gods special was the domain of their powers, and those people would "touch the forbidden sun"?
Either way, in these assumptions these halos should play an important role in harnessing whatever that flame is, only that the importance can range from "particular power boost to do the exploration" to "involved in the process itself".
As a suggestion, the Earth God could give people Halos so they mine and feel the earth better. Giving those to slaves would force servitude and better allow for the job, like a stimulant slave collar, they work down there harvesting the "forbidden sun" forever and ever.
Or alternatively only those that mastered their powers and wills can capture the forbidden sun and bring it out of wherever it is, though the value of a mastered "tiger" power is clearly lesser than that of a "devil" power, so a hierarchy forms, and lesser powers can only submit to greater ones, so a distinction of "demon" and "god" appears.
Of course, all of that happens until the Sun God comes in and changes everything. How he did it, no one can really say, but his powers are intrinsically related to this "forbidden sun". I have exactly one idea, but that's not the point of this post.
In both cases I believe that a symbolism of hell and heaven would fit. Heaven is where the Gods live, Hell is the burning underground where slaves or demons are to work forever.