Where in other worlds the universe had come about through unity, before the shattering disunity took place, this world had been different. There had been no unity to begin with. Even the Codex, despite effort to unite and harmonise all that was within it, was already a shattered and disharmonious thing, at war with itself and imbalanced.
The great being willed it, and the energies within the book coalesced upon each other and the gods were at once pulled towards it. Then the disunited energies of the book were shattered even more, and the shattering disunity took place. 
The Shattering Disunity marked the beginning of the Universe, the execution of the words within the Codex of Creation. At the will of Fate, the Codex was brought to it and the powers of the Codex, the Gods and the Primordials combined created the Universe. Analogous to the Big Bang, the creation of the Universe was explosive and turbulent. An unspecified (although implied to be long, on the order of billions of years) period of time passed between the Shattering Disunity and the formation of Galbar.