Eternal Covenant — K.G. Inglis

Cassie McLennan, a strong-willed university student with an insatiable curiosity, seems to find herself in hot water on a regular basis. When a mysterious Tibetan monk appears in her professor's office, her nosy curiosity once again lures her into investigating. Only, this is one mystery she should have left well alone when she realizes that the monk is murdered and she is the only one who can identify his killers.

Alaric Neumann has lived for hundreds of years as a recluse and is comfortable with his lifestyle. It's simple, quiet, and predictable. That is until Cassie lands herself on an assassin's hit list, and he finds himself in the role of her protector. Without his help, she won't live to see her next birthday. However, the complication she brings into his life is more than just her fiery temper and her infuriating cousin Alex. Alaric's attraction to her is a temptation he is helpless to avoid but claiming his mate could see him banished to the Underworld.