The World of the Dark Angel

From the Introduction: In the Dark Angel urban fantasy series, young seraphim fight a secret war on Earth at the command of elder archangels against the denizens of Hell. With strength, speed, combat training, and the elemental blood magic tattooed on their bodies, they face demonic blades forged from meteorites and hellish magic. With this setting chapter, you can find your own destiny in this ancient struggle as angel, demon, or human.