This is a short story, and a prequel in the Lords of the Underworld Series.
This is an eBook. It is also included in the companion guide Into the Dark (a printed book) along with The Amazon's Curse (Atlantis Series) and The Darkest Prison.
Geryon is the guardian of hell, more monster than man. Kadence is the goddess of Oppression, more angel than woman. Together they will enter the flames to battle a dangerous horde of demon lords -- and discover a passion unlike any other.
Read an excerpt here.