It seems that it may have been an outside creature or collective that helped bring about intelligent life in the universe, and then enslaved it via manufactured creatures called Illithid (or Mind Flayers). After a rebellion, with the Gith leading the charge, the Illithid were defeated, the doomsday device called the Asharus was either destroyed or dismantled, and peace fell over the Planes.
From The Voice of Zerthimon:
In the beginning, there’s a door.
Through the door, the Stranger walks. The Stranger comes from outside the door. The void shimmers, the portal closes. But the Stranger craves doors, needs them, and looks for them everywhere it can…
Billions of years flicker around me like an angry fire. Microscopic prokaryotes rise from the void, emulating the Strange Influence. Fungus grows and spreads, and more Strangers peek through the veil. Cells grow and change and spread. Flatworms. Sponges. Trilobytes. Cancers.
At the very end, I see something new, something complex, the culmination of eons of evolution. A man like me, but somehow younger. Small eyes. Long ears. These Children of the Void, crafted by the dreams of those simple creatures that came before, of their nascent beliefs and cultures. All made possible due to the Strange Influence, a catalyst for the biological evolution that gave them their raw intelligence, their manual dexterity, and, ultimately, their drive for creation and meaning.
The Children’s thoughts and dreams become powerful and their hopes give life to Powers beyond the Influence. Demigods and spirits and magic shape the Void around them, all of these things created at their behest, through their shared beliefs and collective imagination.
The Strange Influence is losing its grasp on the Void, which through the burgeoning powers of the Children and their Powers has taken shape and has become more solid and true than any other part of the Void 1. So the Influence sent the Illithid, and for millenia the Mind Flayers grew in power, enslaving the Children and ruling the Void.
We are no longer powerless to the psychic shackles of the Illithid, and so we revolt. Led by the great warrior Gith, we fight the Mind Flayers on every world. We push them underground, we decimate them, we exterminate their overlords. Nothing less, or our very survival is forfeit.
They move quickly, collecting their power and consciousness into a single Illithid—Erethu Tsathoggua. They hope to escape back to that Far Realm from which they originated and regroup. With the Asharus Cube, a fell artifact built from their own bones and evil magics, they will separate everything back into the primordial components, return it all to the Void, and return to try again. To correct their mistakes.
With the silver sword I forge for her, Gith and our armies chase Tsathoggua to a distant world created during the height of the Illithid rule.
The Asharus Cube, nearly complete, cannot be destroyed. Tsathoggua cannot be destroyed. If either is decimated, the Strange Influence which set in motion all life would become Soggothua 2, and then nothing could stop it from using the Asharus. Because all would be Soggothua.
1 Some interpret this as the beginning of the Prime Material Plane.
2 It’s unsure what this means, but some take it to indicate that Zerthimon (or the author) believed that there is an ancient part of the Strange Influence in all sentient creatures somehow cut off from Tsathoggua, and that by killing the centralized Tsathoggua Illithid, the Influence would reawaken in everyone.