The War between the Archangels of Celestial and the Fallen Angels led by Lucifer ended with the later exiled to Earth. Now talk of war is brewing again, but this time will be different. A weapon has been forged and only one can wield it, but they are neither Angel or Fallen.

Halyn awakes on Earth unsure of what she is. All she has are the memories of her creator, a creature from a place called Celestial. She knows that a war is coming and with the help of Daemon, a human teenager fighting his own demons, maybe they can figure out each of their roles in the war to come.