Limbo.

This is a story of a man who accidentally becomes Grim the Reaper, the most highly revered killer in Limbo. A place beyond time and space as we know it where psychopaths compete for perverse honour and status as they carry out their deathly duties. As Grim struggles to hold onto the memories of the life he's lost, he discovers that the insane being who shaped him (and the course of existence itself) may have sinister plans for the one thing he values most. In Limbo, the end is only the beginning.