Hecate, Queen of the Underworld, takes human form once every two hundred years, coming to earth to marry a man and give birth to a demon child. To do this Hecate must find an innocent to be her groom, put him under her spell and marry him in a sanctified wedding. In this way, her child will grow up looking normal but possessing a demon soul. Those reputed to be Hecate's children are significant throughout history.
The power of a fourteenth century Italian knife called a poignard that bears the inscription "Nic Prius Absistit Quoad Protero Prodicium" (I shall not rest until the demon is vanquished) is the only was to send Hecate back to the Underworld. Her spell can be broken by a declaration of love sealed with a kiss.