User blog comment:Noctosphere/so? who's the first demon?/@comment-31564841-20160809120930/@comment-29408332-20160813084330

@Kajune, God ordered Michael to cast Lucifer out of Heaven, to Earth. He then broke into the Garden of Eden which Gadreel was guarding and corrupted Lilith. Cain is the brother of Abel and they are the sons of Adam and Eve. So, they were most likely born around the same time as Lilith. I believe Lucifer was going to corrupt Abel somewhere around the time after corrupting Lilith, but Cain offered himself in exchange that Abel go to heaven. Lucifer agreed, but as long as Cain was the one who killed Abel. (This was all said in the show, for comfirmation.)