After Lilith left it took years for Lucifer to move on, but eventually he did, falling in love with a human sinner who earned their place in hell by being a witch in their life. Living in canablism territory they developed a mild taste in blood. After mentioning one night that his blood is different than a humans you asked if you could tease, however the act of being the first human to drink angel blood cursed you for eternity into being the worlds first vampire.