The Movie starts with you learning about Legion, a collection of demonic souls that have escaped from hell, Cain a knight templar is duitied with the task of destorying the souls, and he believes he does.
The movie skips to present day where we learn a little about Ryu a assassin from an ancient warrior priest family sent to the City of Angels to finish his targets only to find out that some of them are Oni.
Your introduced to Max, a hitman rendered soulless after dying for 20 minutes and his body returning to life. Hes hired to wipe out an opium den, unfortunatly for him its filled with the possessed.
The story of these three men is intertwined when the demonic souls try to create a portal to hell with which they can summon minions of demons to lay waste to the land, and only they can stop it.