The present and the past are tied together within a single soul belonging to a witch of noble heritage, but unaware of her own title as she grew up thinking herself to be nothing more than a human. It was only the demon prince that knew her old soul who brought her illumination, awakening inside her feelings that weren't entirely hers, but a being's more ancient and much more feared.
As Seraphine is revived within Lucia, the one with whom she shares body and soul, and is crowned in the name of the Beast with the sole purpose of fulfilling her own promise made long ago with the goddess of witches, Ethan also takes on the name of the Beast, but in order to gain power and fulfill his own ambitions, one of which is rewritting the tragic story between him and the high witch as he tries to stop history from repeating itself.
But the Beast rose up from the sea of souls, made up of Seven Crowned Kings and ten domain-less kings that bear the names of blashpemy. Because everything with a beginning must have an end, they kept on existing, eager to fulfill the oldest promise of the world. While both Hell and Heaven split up and join the final war caused by the Beast, the Seven Kings each understand more about the atonement and punishments that fell onto them for sins that weren't theirs.