Selena is a would be black magic practitioner who gains real magic powers after obtaining a mystic Kryptonian artefact.
History
Supergirl
Selena was a power-hungry would-be black magic witch assisted by the feckless and long-suffering Bianca. One day Selena discovers the Omegahedron, an ancient Kryptonian artefact. Whilst not knowing exactly what it is, Selena quickly realizes that the Omegahedron is powerful and can enable her to perform real magical spells. Selena fell in love with a boy called Ethan. She drugs him with a potion to make him love her. However, Ethan regains consciousness while Selena was away and wanders out into the streets. An angry Selena uses her new-found powers to animate a construction vehicle, which she sends to bring Ethan back, causing chaos in the streets. Supergirl rescues him and he falls in love with her instead.
Supergirl and Selena fight with one another, until Selena uses her powers to send Supergirl into the Phantom Zone. Meanwhile, Selena misuses the Omegahedron to make herself the "Princess of Earth", with Ethan as her lover and consort. After escaping from the Phantom Zone, Supergirl regains her powers and has a final confrontation with Selena. Supergirl defeats her and exiles both her and Bianca to the Phantom Zone.