Devil's Assassin: A Collective World Novel. Lucifer's War, #2

Does she have what it takes to be Satan's assassin? Lucifer longed for the day Lilith would stand at his side. That day has come. It's not all sunshine and hellfire. Together they face a road paved with demon uprisings and betrayal. Fallen angels and High Demons oppose them at every turn. When Hell's deadliest souls are released from their sealed prison by Lucifer's twin brother, Lucifer fears for the safety of his family and all of humanity.
He can easily guess what it is that Sammael seeks. Luckily, the item his brother will stop at nothing to find is safely tucked beyond reach, and Lucifer intends to keep it that way. For Lilith to grow into her full powers, she must come to terms with the drastic costs involved. Bloodthirst and vengeance are just the beginning. Being a vampire is difficult enough, but now she must be the devil's assassin, eliminating the evil that threatens to unleash Hell on Earth.