You're the Shadow Man , a person who can switch between the world of the dead and of the living. In the world of the living, your mission is to prevent five serial killers from bringing about Armageddon. When you die, you are transported to the world of the dead and become Shadow Man once again. This means you're not really mortal in the world of the dead.
In the world of the dead, your gun shoots ghosts which kill zombies and other creatures that live there. You also have different voodoo powers and weapons at your disposal. Additionally, you're carrying a large inventory with you.