Immortal Promise — Lietha Wards

Lucas Edwards was a vampire; a vampire who was destined to be the leader of his race. He kept the legion in line and there wasn't senseless slaughter for centuries. Yet, there was some unrest among his kind. Some vied for the power Lucas held claiming he was too sympathetic toward the human race. Lucas, had no intention of allowing that to happen and was able to maintain his position for centuries.
That is, until he got distracted.
There were emotions he'd buried deep that he'd forgotten even existed until he met a young medical student named Elsa. Her innocence and intoxicating lure awakened something within him that threatened to bring his rule to an end.

note; there are some graphic scenes, sex, and language.