The Underground City (Lily Harper, #2)

Her newest mission will see her traveling to the sewer aqueduct of the Underground City and later, the prison. But, luckily for Lily, she’s got the hunky yet antisocial bladesmith, Tallis Black, by her side. And quite possibly unluckily for her, she’s also got her guardian angel, Bill, who’s up to his old, foul-mouthed antics.

Between learning how to wield her sword, personal training with a hot-headed demon, traveling to the Underground City not one but two times and discovering that the leader of the Underground City harbors a curious fascination with her, Lily’s hope was abandoned a long time ago.