Ghoulmari
It lives within; taking every motivation, everyone wants and need, every second of our lives, every part of us who wants to live. The dream world is the only place where we're free to run because when we wake up, reality has us sewn to the bed. Our thoughts captured by the demon within, saying it will love us once we join them after death.
To the point:
A shadowy entity is a depression lingering on people, but hell wants it's own savior to bring up the fiery pits. Taking a demon named Maria, she becomes a human for the first time and kills people for a sacrifice to bring up former angels who are now considered demons.