In Christian mythology, Eve was the second woman created by God (Lilith being the first). She lived in Eden with her husband, the first man, Adam. Eve was beguiled by Lucifer to eat from the Tree of Knowledge, even though God had forbidden to eat the tree's fruit. When God returned to Eden to find Eve wearing clothes, he realized that she had eaten from the tree and was cast out of Heaven and left on Earth. She later lived out her life and died as a mortal woman.
In PainkillerNow dead, Eve has been wandering Purgatory longer than anyone else. According to Lucifer, she had escaped Hell (which would explain how she knows so much about his armies). After his death and killing the Necrogiant, she meets Daniel Garner in the Enclave, he treats her with hostility and near gun violence and tries to offer her help to try to locate Lucifer's armies. After Daniel killed Swamp Thing she is concerned about his wound but he says he is fine. He still keeps her at a distance, ignoring most of warnings and fears, until Lucifer kidnaps her and takes her to Hell. Daniel rescues her after killing Lucifer in his demon form, however, the fall knocks her out. Daniel fights off a horde of demons while she stays unconscious. Eve acts as Daniel's ally throughout Painkiller and Painkiller: Battle out of Hell, giving him new information about troop movements and contacting allies to find out additional details.