Queens of Ruin: Chronicles of Mahon Book Two Brenda Murphy

Secrets. Lust. Betrayal. The city of Justia has fallen, and Lilith, goddess of fire, is missing. All that remains of her once-powerful empire is an abandoned castle haunted by spirits.
Newly freed from her crystalline prison, Mara and her warrior consort, Reika, are on a quest to find Lilith and restore the empire of Mahon.
After their mission is betrayed, a time-traveling sorcerer kidnaps Reika leaving Mara trapped in the tunnels beneath Lilith’s ruined castle. Unwilling to surrender her love or her life, Mara risks all to save her mate.