Ardra's "magic" - which turned out to be part of an impostor's con-game.
Ardra was the Ventaxian culture's version of a devil. Her mythical evil qualities led her to be compared to the Human character of the Devil and the mytho-historical Klingon avatar named Fek'lhr.
According to legend, the Ventaxians were granted a thousand years of peace in return for becoming Ardra's slaves and having their riches given to her.
In 2367, she was impersonated by an interstellar con artist. This impostor deceived the Ventaxians into believing she was the deity by using technology to mimic various phenomena believed to herald Ardra's return. Her ruse was revealed by Captain Picard when Lieutenant Commander La Forge discovered her ship in orbit, which was commandeered by the USS Enterprise-D's crew. (TNG: "Devil's Due")
Ardra was portrayed by Marta DuBois