Imp Forsaken (Imp, #5‪)‬

Sam is banished to Hel, the bond with her angel, Gregory, broken.  Six Elven kingdoms are battling for supremacy, and she’s broken and injured in the middle of the most hostile one.  Shooting the top off a royal throne, committing fraud in the completion of a contract, and threatening a high lord hasn't endeared her to the elves, either.  If she wants to free the enslaved humans they hold, she’ll need to find a way to help unite their kingdoms.

But elves aren't the only problem facing Sam.  The ancient demon, Ahriman is holding her to the terms and conditions of the breeding contract she signed – and one thousand years under his claw is looking to be the most terrifying thing in all of Hel.