Ovid says of Cardea, apparently quoting a religious formula: 'Her power is to open what is shut; to shut what is open.'
The goddess of thresholds and especially door-pivots (cardo "door-pivot"). Just as Carna she is also a goddess of health. Cardea is the protectress of little children against the attacks of vampire-witches. She obtained the office from Janus in exchange for her personal favors.