Primordial Light and Darkness

Going by either their full title or simply the Light and Darkness, this pair of ancient powers, the Primordial Light together with its counterpart the Primordial Darkness, personifies the abstract ideas already present when the universe began. Once the source of all creation was divided, these paired essences became the bedrock from which the opposing camps of the Rulers and the Monarchs took shape. From a remote, alien dimensional plane the Absolute Being came, fleeing his own Itarim kind, and at the outset he found nothing but these two forces locked in perpetual struggle.

To bring order to that chaos, he built the cosmos and called all things forth, carving each primeval essence, the Light as well as the Darkness, into eight shares apiece. From those shares came the Fragments of Brilliant Light, who are the Rulers, and the Monarchs, every one an avatar of its essence and doomed to butcher its counterpart in unending war. No vessel can bear more than a single essence; the overload would destroy it. One sole exception exists, and that is Ashborn, who reigned as the very first Monarch of Shadows. Dreading his creations, the Absolute Being hid an all-erasing power, the Primordial Darkness, within his most faithful Fragment, who already held the Primordial Light. Carrying both turned Ashborn into a being of genuine duality, a Fragment of Itarim capable of driving back the Itarim themselves.

Although they were first shaped to act as heaven's emissaries, the Fragments of Brilliant Light came in time to revolt at their maker's cruelty, rising as god-slayers and at last killing the Absolute Being. Each time a leader dies, the essence inside hunts a new host: a fallen Monarch's Primordial Darkness goes back to Nidhogg, the eight-headed serpent that guards the World Tree and keeps watch over the Darkness of every dead Monarch. Any would-be successor must beat the serpent and survive its trials to inherit a chosen predecessor's power. Through the System, Ashborn's legacy and twin essence ultimately reached Sung Jinwoo, raising him into an existence that outstripped even the one before him.