The Unredeemed - Walker Luke

In the ultimate battle between evil and evil...only one can win. Four hundred years ago, Benjamin Harwood butchered whoever he saw fit to kill, knowing that sacrificing his murder victims to a demon would keep him safe from eternal punishment. But now, their agreement has been torn in half and the demon is coming for Harwood's soul, coming to set him to burn. Preparing for war, Harwood gathers the worst of the worst, the monsters and murderers he calls friends. With this group of damned killers, Harwood must return to the crimes of his past and seek help from his most recent prey: a teenage girl whose family he destroyed, a girl with more reason to loathe him than anyone in his life or death. Only then he can try for a redemption that may be impossible or face a universe of suffering. But Harwood doesn't know there is a hole in the floor of the world. And something much worse than the dead is down there...