Hekaté Hecate is a demon who comes to earth every two hundred years. Her goal is to create a demon spawn, which she does by finding an innocent, putting him under her spell and marrying him in a sanctified wedding. She has to be impregnated by a mortal man so her child will appear human but be pure demon on the inside. The spell can be broken by a declaration of love sealed with a kiss
hecate was sent back to the underworld by the power of a 14th century italian knife called a poignard that bears the inscription "i shall not rest until the demon is vanquished." and hecate is in the series 'the wedding from hell'