Daphne Atreus, Helen's mother, is the only mentioned Scion who has the Face along with Helen. She abandoned Helen and Jerry when Helen was a baby (for Helen's own good), but reappears in Starcrossed.
Daphne is mentioned to be conniving, manipulative, and a liar. She tricks Helen and the Delos family into thinking that they're related. Since Lucas, the only Falsefinder in the group, was out of the room and instead told by Helen, Daphne's lie wasn't picked up, proving that she knows exactly how to work situations. In the last book, Daphne reveals her master plot. She kept Lucas and Helen apart because, in essence, she thought Orion would be the new Hades because he looks like him, and Daphne would be able to be reunited with Ajax -- whom she loves with an almost scary dedication/desperation to be reunited with.
Helen notes that there is nothing where Daphne's heart should be- only black nothing -- for Daphne had traded all of what had left for feelings with Hecate (a Titan) so she could kill Tantalus; and in killing him, avenge her beloved Ajax's death.
Daphne is completely obsessed with her husband Ajax, and revenge on Tantalus, who she blames for Ajax's death.
Daphne also has the Face. She has the other half of the cestus, which makes her able to change her appearance at will and seduce any man she chooses -- thus able to control him. Whereas Helen has the part of the cestus that makes her impenetrable to any weapons (from forks, to bombs, to sticks).