The Dark Aurora exists through the Fibrill, a type of power force, of Nereid. In contrast, the Divine Aurora is the divine manifestation of power belonging to Seyfert, the god of creation who fashioned the planets of Inferia and Celestia. Ten years prior to the game's plot, Shizel suffered the lost of Balir, her lover who shared with her an ideology of a realm beyond reality with no pain or suffering. The tragic event was a result of political upheaval involving the death of the late Celestian king and a subsequent betrayal by Shizel's brother Hyades. Balir reminded her of their shared goal before dying in her arms, the moment in which Nereid broke free from his imprisonment by Seyferts and seized Shizel, who submitted to the unknown power and became Nereid's host. Shizel's hatred for the material world combined with Nereid's desire to destroy Inferia and Celestia, which would restore Vatenkeist, the spirit world of Nereid, in the process.
This ultimately manifested into the power of the Dark Aurora, which Shizel then used to annihilate Luishka and nearly everyone around her during the event. Hyades and Meredy, Shizel's daughter with Balir, survived this event due to their shared bloodline now being aligned with the Fibrill of Nereid; however, Shizel herself took the opportunity to conduct cruel experiments on the two in her efforts to better understand the Dark Aurora and control it, all while acting under the steady corruption caused by Nereid. Hyades eventually went mad due to the experiments, as well as guilt for his betrayal, while Meredy one day managed to escape with the help of the researcher Galenos, later settling in Imen. Meanwhile, Shizel seized power in Celestia under the guise of Balir, using the Dark Aurora to form a barrier around her castle in the sea.
During the events of the main story, Reid Hershel and his companions, seeking to overcome Shizel's Dark Aurora, complete the Trials of Seyfert in order to obtain the Divine Aurora, which can be used to counteract the Dark Aurora. They eventually succeed in overcoming Shizel in her castle, ultimately preventing the Grand Fall that threatens the world from occurring by using the Divine Aurora in tandem with the Dark Aurora, separating the planets of Inferia and Celestia, thereby permanently preventing the threat of their collision. Shizel, along with Nereid, is sealed within the Seyfert Ring's core before the Orbus Barrier ruptures, reconstructing reality so that Inferia and Celestia remain separated.