The Elemental Chaos is just that. Chaos… in its most pure form.
During the Arcane Divergence (The War of Heavens) the reality of the 5th dimension would be sundered to such a degree that even to the powerful primordial beings that existed at this time, the 5th was almost inhospitable. Many powerful beings had created or inadvertently manifested realms of their own that reflected their pure desires and intentions, however much of the Etherium remained in a state of utter mayhem and it would remain like this for an unknown period of time.
Eventually however something was created from deep within the chaos, and a mammoth object of almost blinding radiance would come into existence to push back against the turmoil. The Lifebringer is a strange and wondrous creation, seemingly providing all that is required for life to thrive… but it can only do so much. Its radiance has done a great deal to provide stability and tranquillity to the winds of the Etherium and has given rise to the Bastion as we know it today; but the Elemental Chaos is still out there. It has no desires or consciousness of its own and yet it seemingly seeks to envelop the Lifebringer and the Bastion with it, being somehow drawn to the space where the ever-bright creation now resides. Its reach is invisible, but to the mortals of Bastion its presence is extremely real and tangible… all you have to do is travel to the edge of an Isle. When you look down into the fathomless depths of the Etherium you can’t actually see the Chaos… it's much to distant for that. But you feel its pull, its reach and desire to drag everything that exists back into its waiting maw.
And so an equilibrium is struck, between the Lifebringer's radiant hold on it's lands and the Elemental Chaos’s ever present gravity. To the living mortals of Bastions Isles these forces are on such a scale that an observer might struggle to even comprehend such ideas. But these forces are what have been able to give rise to the world and Radiant Era as it exists today. The light and the darkness, together they provide a sense of stability and understanding, even though that perception may be misplaced and far from the true nature of the Etherium.