Brimstone Angels

Brimstone Angels is the first novel in the Brimstone Angels series by Erin M. Evans. Originally it was the first in the Neverwinter series, which never surfaced.

"Havilar and Farideh are twin tieflings abandoned at birth and raised by dragonborn. Careless Havilar has an innocent soul and a penchant for trouble, and careful Farideh feels the weight of the world, her tainted bloodline—and her sister—on her shoulders.

In a summoning ritual gone wrong, Farideh ends up bound in a warlock's pact with a handsome but sadistic cambion devil, and they are thrown out of the village. A lone dragonborn accompanies them out of compassion, and the three adventurers, often perceived as monsters themselves, begin to make a name for themselves as monster slayers.

But once they reach the encampments in the ruined city of Neverwinter, their simple plans of slaying monsters to make a living get tangled up in a devilish snare six layers deep. It will take every ounce of the twins' skills—and some borrowed besides—if they are to have any hope of staying afloat in the deadly designs around them."