Originally Posted by
Anonymoose
This will probably require a thorough explanation of the cosmology as a whole, so bear with me here.
It is implied that when formless chaos was given order and existence came into being, the aetherial sea gave rise to Light and Darkness, personified by Hydaelyn and Zodiark. The story we've been told - which may or may not be complete or accurate - is that the Darkness is by nature lustful of power and dominance. When Zodiark tipped the balance and took power for himself, Hydaelyn grew fearful and expelled him.
Dividing the original cosmology into planet and moon stressed the fabric of the universe so severely that it caused spatiotemporal rifts (cracks in spacetime) that resulted in reflections of the world fanning out in all redirections - thirteen "copies" in total. How alike these worlds are is unknown.
In order for Zodiark to be made whole - to be reborn - the cracks must be healed; the reflected worlds need to be rejoined to the original dimension (aka The Source). The Ascians labor to accomplish this by creating Calamities, weakening the barriers between worlds with great acts of chaos and destruction in such a way that the reflected world is destroyed; all Life there is killed (reverted to aether), and rejoined to the Source (empowering Zodiark). Hydaelyn protects against this by empowering Warriors of Light to thwart their plans.
The reflected worlds all have shards of Light and Darkness, but in varying amounts. The catch is that if either becomes too dominant before a Rejoining occurs, the aether is destroyed by the flood of Light or Dark and leaves only a void in its wake. This is where Elidibus' mission deviates from the Ascians in black; his mission is to direct the chaos and prevent the rocking boat from capsizing, so to speak. Zodiark cannot be reborn from void.