They didn't make the universe, but they sure made the world. Pics definitely required on this page.
Kjelchaikhan was the first. He was born from the corpse of Creation at the beginning of the universe, and he made his body from the flesh of Creation. Kjelchaikhan used the latent arcana in the aether to create Aphelion from nothing. What he made was an inhospitable, partially-molten hunk of blisteringly hot rock. There was nothing on it, and he didn't care. Satisfied, he went to sleep for a very long time.
Kjelchaikhan is the most involved of the elder gods in mortal affairs, but even then he tries not to foster dependence and is quick to remind his worshippers not to waste his time. He enjoys ambiguity and loves to give cryptic instructions to his followers without elaboration. He also likes to lie, seemingly for the sake of it.
Tsenmaer was born next. She made her body from the blood of Creation. It's unclear when she was born in relation to Kjelchaikhan, because no one existed to maintain linear time just yet. Either way, she took over while Kjelchaikhan slept inside of a volcano. She created all the water in every ocean, sea, river, lake, and all that sneaky miscellaneous water too. It rained until the surface of Aphelion was eaten by the sea. Then she decided her job was done and she went into the deepest trench in the deepest ocean and went to sleep for a very long time.
Tsenmaer is the least involved of the gods. She rarely communicates with anyone, mortal or otherwise, and she is often arbitrary if not outright cruel when she finally does. She largely holds the sentient races in disdain and prefers the "lower" races of plant and animal.
Then Archaeos showed up. They made their body from the bones of Creation. While Kjelchaikhan created the masculine and Tsenmaer created the feminine, Archaeos took both, and gender was fake from here on out. That out of the way, Archaeos built the sky and started the wind. As air filled the world, the offal of Creation went to Aphelion to become the first mortal beings. But Archaeos's job was done, and they surveyed their skies. To this day, Archaeos flies at the end of the air, where the sky becomes the aether. They watch Aphelion in a meditative trance, and will occasionally come to roost on the enigmatic Sky Pillar.
Archaeos seems largely unbothered by the affairs of mortals at all, though they've chosen to impart wisdom to a select few. But for the most part, they enjoy watching the natural processes of Aphelion carry out unimpeded. To a point.
The fourth god is not real and has no name. It is a cautionary tale, though the message is not well understood and poorly told.
The fourth god is no longer real and can never be named. Naming it might give it power, which might bring it back. No one knows how the fourth god was born, but it probably didn't come from Creation. The fourth god thought Aphelion was flawed and ugly, the fourth god thought the universe did not fulfill its potential. The other three gods know that the universe is imperfect, because it is made from pieces of a being achieving perfection, and perfection cannot be achieved until Creation rejoins all the imperfect pieces. The fourth god said that's horseshit and started making a new universe. Shadowside. Shadowside was even less perfect, and the fourth god petitioned the other three to break down the universe and use its energy to achieve perfection for Shadowside. The other three had a quick meeting and decided to uncreate the fourth god. Kjelchaikhan was decided as executioner, and he erased the entire god- past and present. He didn't know how to do future. Unfortunately, when he uncreated the fourth god, he destroyed it from everyone's memory but his own. He tells this story as truth and literal happening. Tsenmaer and Archaeos are quick to remind that Kjelchaikhan loves to tell lies.
Whether the story is true or a fable dressed up as true varies across the three major religious cults. Only Kjelchaikhan's cult believes the fourth god to have actually existed. Interestingly, the Shadowside entities very much believe in the fourth god. But then again, they also actively hate the three gods of Creation. A lot of them seem to hate Creation, too. So who knows at this point.