It’s common when discussing such things to start with “In the beginning” or some other such phrase. However, the universe will be much easier to understand if you throw away such concepts of beginnings and endings. They are uniquely mortal frames of reference, perhaps it is because we are mortal that we cling to the idea that the universe had a beginning and will have an end.
The universe has always existed and will continue to exist long after no one is left to remember it’s current configuration. All that is sprung out of the Primordial. After a millenia, or maybe it was only a moment… time is a construct as well, of swirling chaos, the chaos gained conciousness. It’s uncertain if this conciousness was alone or if several such motes of awareness came to be all at once or even if they each evolved at different speeds over time. It’s even possible a single conciousness existed and eventually fractured over time, as things are wont to do in the Primordial. What is accepted is that these beings were the first to establish order amid the chaos, though they did not do so deliberately. They are the Grael and are the source of power by which Warlocks access the primordial chaos.
The Grael strove against one another for dominance and, thus, the Planes were created. They did not do so directly, but imagine two giants equally matched, each striving to throw the other to the ground in a hurricane. Locked in their positions, each looking for an advantage, the space between them becomes calm. The winds are blocked by their massive bodies and the rain is less severe. It is this sort of contest of wills over control of the primordial that give space for our reality to thrive.
The Planes, much like the Primordial before them, were untamed energy. From them sprung the Pantheon of Gods. Some scholars believe it happened over millenia and others believe that the arose from the blood of the Grael as they sustained injuries in their conflicts… if such beings do in fact bleed. Whatever the case, the Gods saw the conflict caused as the Grael fought for supremacy and chose a different path. They, at least initially, worked together to bring order to the Planes. From this order did life as we know it eventually evolve and the Gods chose their homes in the planes which they found most appealing. Gods rarely interfere in the lives of mortals anymore but, when they do, it’s almost always to settle a disagreement over whose plane of existence is more essential. The power of each God is at it’s greatest in their own demesne. Since there is rarely direct conflict between them, they travel freely between the Planes, but even they tread lightly in the Primordial.
There is much debate as to why the gods are sorting souls from The Fae Realms and Material Plane into the Astral Plane or the Nine Hells & Abyss. Many believe it’s a system to maintain balance in the universe while others believe it’s simply a way for the gods to reward or punish mortals for not worshiping thier ideals in life. There could certainly be more written on the subject…
It may seem unusual to include Astronomy in a discussion about religion, however the alignments of the Zodiaks of Yggdra are instrumental when traveling between planes that exist within Purgatorium. It’s even said that the Gods elevated paragons of their ideals to be constellations as an eternal honor.