This is a guide to how Universes work as a whole. This does not detail their individual governing systems or how they act in accordance to those, but how they work in a general sense.
Omnipotent Beings, their Roles and DutiesEdit
In each Universe, fifteen in total, not just alternates of the same one where roles are somewhat adjusted but follow the same overall progression, there is an omnipotent being(Indeed, multiple beings possessing all power, fancy that logicians and book keepers) with jurisdiction and power over their creations to an extent. Why to an extent? Will and presence. To be more specific, the individual's will and decisions and the omnipotent being's presence and activity or lack thereof in the universe in question. If a being chooses to disobey the omnipotent being in charge of their universe, they may be punished or let be based on the presence and choices of the being overseeing them depending on the severity, if any, of the disobedience. More distant omnipotent beings are less likely to interfere or punish those the are watching over, while more present omnipotent beings are more likely to act based upon their will should they see disobedience in those they oversee. This brings us to the roles of the Omnipotent beings in universe: To oversee and guide their creations to a reasonable extent while nurturing the ideas of free will to an equally reasonable extent, both of which are up to the discretion of the being in question, while also maintaining the Veil, a topic for another day. They are not supposed to hand hold or constantly scrutinize their creations, but that does not mean they cannot have an active role in their creations' lives. This is their role within their universe, outside of which they have very little influence due to the willing separation of universes by the omnipotent beings in charge. Granted, these minor bouts of influence, while they do cause similarities in universes serve to further alienate the universe from one another as they do not want unwanted influence in their universes.
This does not mean that they cannot or choose not to communicate, more so that the Divine Powers, as they have been coined, have different values from one another, which could easily lead to disruption if they were to try to correct what other Divine Powers had set within their own universes. As such, the Powers themselves stay within their universes and generally keep to themselves, but may occasionally choose to contact the Power of the other universe. Their denizens, however, through strength, technological advancement or divine providence may gain the ability to move between universes, but this is moderated heavily from within the universe in most cases because this can almost be as problematic as the Divine Powers interfering with one another, if initially on a much smaller scale. This is comparable to bringing a new species without predators into an ecosystem where nothing could prey upon it. Continuing this train of thought, the Divine Power of the visited universe would have no jurisdiction over the visitor and, thus could not act without sufficient reason to do so and an affirmation from the visitor's Divine Power as to prevent unnecessary backlash or interference. For example, someone from universe A enters Universe B and decides they want to take over it. The Divine Power of Universe B notices them and watches their actions to gauge whether or not to act and, upon reaching the decision that they should indeed act, they contact Universe A's Divine Power and tell them that they are going to act and want their input on what to do in specific (i.e. smite, send back, wait for another to be sent, etc.) then act based on that. This, in turn brings us to the topic of Divine Retribution or, more simple put, smiting.
Smites and YouEdit
Smiting, or the act of exercising one's divine power in such a manner that it strikes an individual or chosen group, is a right reserved specifically to the Divine Powers of universes. Less powerful beings may develop arts akin to the Power's Smite, but this is simply a pale imitation of the true thing, a strike of power beyond mortal and godly comprehension that takes all of which that the universe is and its the chosen with it. This may sound simple and easy to comprehend, but in truth, this is easily the most powerful destructive action a Power can take, cleaving through their fold of existence with a speed faster than instantaneous if they were so inclined, ignoring the resistances and strengths of the chosen in addition to afflicting the chosen (if they weren't outright slain by the strike due to the Power's will) with something that best represents the nature and will of the Divine Power in question if they are a denizen of the universe in question. If not, however, Smites take on a different property. Smiting in one's own universe, as the Divine Power, generally strikes down the chosen. If the chosen is from another universe, however, it strips them of their Divine Protection(a resistance to all of the visited universe's attributes and effects granted by travelling across universes). In MOST cases, this is a permanent removal unless the other Divine Power chooses to reapply it or the target can resist or negate the effects of a Smite, of which there are a countable few. Fewer still are those who can fully resist Smites and ignore them, of which five are known, these five being those who can traverse the different universes at will, with them having to greatly dilute their presences to even materialize within universes should they enter places that are not their domain.
There is one other exception to this rule: Beings that adapt to universes they enter, becoming "denizens" of it. They are not within the Divine Power's jurisdiction, but the Divine Power may freely act upon them as needed. They lack Divine Protection so, handling them is easier and can, in most cases, be left to the actual denizens of the universe should conflict arise. This would be akin to an invasive species being introduced to an environment, but having beings that could prey upon it in said new environment, strength permitting of course.
Angels, Demons, Gods and where they Fit in the Big PictureEdit
There are the Divine Powers, the top of the pyramid within their universes, there are the forces of Chaos, Order, Balance and Magic, irrational existences that permeate the universes and maintain the Veil within each of them. And then there are the lesser Gods, Demons and Angels of their equivalents. These sit at the lower end of the so called Divine Order, well above simple Mortals, but far from the heels of the Divine Powers. In most cases, gods and goddesses are manifestations of the Divine Power by mortal comprehension, given set roles and abilities they govern. Minor Gods require worship to sustain themselves, Greater Gods do not and have awareness of the Veil, which they can shift. Angels and Demons, though often in opposing positions, serve as the messengers and emissaries of the Divine Power, directly or indirectly. Angels often act as the direct messengers of the Divine Powers and occasionally the Greater Gods, but also as their swords and shields should it be required. Demons, in most cases are to be the trial for mortals to overcome should they become to complacent or self-centered, appearing like a sudden scourge and vanishing as quickly when given the call to return. This is not to say that neither Demons nor Angels have wills, but instead have roles granted to them that define their interactions with mortals and the like. In some cases, the equivalents of Demons and Angels live among ordinary mortals, lacking their roles and allowed freedom of choice. In others, either side helps or opposes mortals as a great trial or as an attempt to spur them forward by decree of the Divine Powers. In the rarest of cases, however, both are long gone, with only relics and specters of them remaining.