Philip Stark was a serial killer that was brought to the attention of the Phantom Stranger. Rather than simply killing Stark, the Stranger absorbed him, destroying Stark and assuming his identity due to Stark having a loving but unaware wife and kids. Stark had intended to murder them as well, believing they were too good for this world. The Stranger, forever lonely, couldn't allow Stark to kill his family as he normally would have to and took over Starks place and life instead.
Stark was scattered throughout reality, and managed to put himself back together in another dimension
Sin Eater was created by Phantom Stranger writers Dan Didio and J.M. DeMatteis, as well as artists Michael Paz and Philip Tan.
Unable to take back his life, Stark instead chose to take revenge on the Phantom Stranger by kidnapping his family.