Overworld Underground Series

Emily Glass thought a move to Atlanta was just what she needed to jump-start a new life. But after her roommate and best friend is attacked by a man with superhuman strength, she discovers an underworld to Atlanta she never expected. Recruited by a strange organization with an enigmatic agenda to help apprehend the attacker, she soon finds herself doing strange side jobs for them. To make things more complicated, the boss at her day job expresses romantic interest. 

During a routine Custodian investigation into illegal activities by vampires, Emily Glass discovers a massive demon-summoning pattern in a warehouse. Her demon-possessed boyfriend, Tyler Rock, identifies it as a demonicus - an ancient pattern used to summon demons from different levels of hell all at the same time, with the most powerful demon devouring the souls of humans to magnify his power.

Dead in Days. Emily Glass will be dead in days unless she can overcome destiny. An overlord of Hell has a price on Emily's head and every demon in the underworld wants to claim the prize. She might be the Great Banisher, but even she can't fight off an army of demons. The only way to survive might be to trust an enigmatic Seraphim, and to find the source of her powers. Where does her demon banishing power come from? How can she rip the powers from vampires?