Warrior Mage by Nancy Northcott

A Woman Tormented by Darkness. A Man Sworn to Oppose it
The Fate of the World at Stake

Archaeologist Audra Grayson hopes this dig will save her career. But that hope is dashed when she finds strange relics and a brilliant, sexy consultant comes to investigate her for fraud. Worse, the evil shadow that has haunted her for years is growing stronger.

Mage loremaster and archaeological investigator Will Davis senses the darkness in Audra when he comes to authenticate her work. Worried she’s allied with the enemy, he vows to ignore his attraction to her. Then deadly ghouls target the dig, seeking the ancient relics to open a portal for demons. If they succeed, everything on Earth is doomed.
With ghoul attacks escalating, time is running out for Will to stop the portal from opening. The chemistry between him and Audra threatens to combust, but the darkness within her may give the enemy its chance. Even if he can save her, can he trust her? His parents are famous archaeologists, and women have tried to use him before. Is she a demon pawn? A user? Or the answer to all his dreams?