Dream of.. More Sepia-toned than Black?
I had a dream of a universe similar to "Darker than Black." Similar, but much the same.

There was this woman- a fire user, who had just fubared a mission, and she was in a bad mood. She had straight, neck length light brown hair and a somewhat innocent face. She was meeting with her "boss" - a in his twenties, somewhat messy brown haired closed eyed smiling archetype. He reminded me of a calm and collected version Saya's brother from Blood Plus. Another person was coming, who I think owed the boss money. He asked her to to help out with the person in question, so she hung around for a few minutes and sure enough he showed up. The other guy shows up. He had smooth black hair, and is dressed in an immaculate tux. He's moving aggressively, so she makes fire form in the air in front of him. He sidesteps the fire at "near instant" speeds, and then "demons-out." His features become more angular, his teeth extend, small horns form, his eyes glow with internal light, fire wells up around him and he says "How around some real fire." in an anime demon voice, and the fire wells up around the girl.

at this point, I'm given some of the rules of the universe. The more of their power they use, the more like a demon they look. Fire burst around her and it was intense- but he had to be about maxed. People are resistant to the element they use- resistant, but not immune. Their resistance is related to how much of their power they release, and it takes as much power as their opponent is using to neutralize an attack. She doesn't dodge. Doesn't move. The fire wells up around her and she says perfectly still. Then, her eyes start glowing. Nothing else. The smallest fraction of her power. The guy stops, appropriately cowed. He realizes that if she attacks there's really nothing he'll be able to do. It took him that long to realize he was attacking someone who's power was as much above his as his power was above a normal humans... At least.