Dark use to live on earth as a human with a husband named Mark and a baby but one day his human form snapped and he reveled himself as a shadow powerful demon from the underworld and Mark left him because he had hurt his human boss as he was getting sick of him trying to make his life a living hell and Mark was scared that he will hurt his baby so he ran away from dark but Dark didn't like that because he wanted his family so without a thought he took over earth and made Mark stay with him with their baby..start from there
