Long ago, during Archangel Lucifer’s attempt to usurp Heaven, he sequestered the angelic part of his spirit into a jewel. This spirit, after falling to Earth and becoming trapped in a chalice, later becomes known as the Sangreal, or the Holy Grail.
Throughout its time on Earth, the Sangreal observes humanity and waits for an enlightened human to return it to Heaven. However, after a millennium passes, Lucifer decides to regain the Sangreal to make another attempt to conquer Heaven. In Britain in the Middle Ages, Lucifer conceives a son with a human woman who he plans to sway to retrieve the Sangreal. The boy is named Merlin.
Michael too conceives a child with a human, a daughter named Nimue who he hopes will befriend Merlin and turn him away from evil. Although their powers and motivations are quite different, the lives of Merlin and Nimue converge with the Sangreal, initiating a legendary age with these half-Archangels working magic in the shadows. Yet Lucifer, as well those under his influence, threaten the Sangreal’s attempts to return to Heaven, along with imperiling the lives of countless others ensnared in his plots.