I'm not into most urban fantasy, and heaven vs hell is also not a genre that usually grabs me, but I am a sucker for a well defined magic system. In Dread Uprising, if someone gives their life for another, then there is a chance they can be re-awakened as an Ash Angel. If their ashes are spread at the location where they were killed during the summer solstice, then there is a chance they will return as an Ash Angel. This is exactly what happens to Trace and he finds himself thrust into the eternal struggle against the Dread, who are created in a similar but opposite way. A Dread must have killed someone else while alive, and then the dust of their remains must be taken to the location of the murder. Ash Angels earn divine gifts known as bestowals, which are powers they may use against the Dread, and after 7 bestowals they ascend into heaven. Despite these powers, for the first time in history, the Dreads have the upper hand and the Ash Angels now find their numbers greatly reduced.
Dread Uprising - a fresh take on the war between heaven and hell