this is the third story in the Immortals series.
Kaderin has been killing vampires for two thousand years, when one day, she finds a vampire she can't bring herself to kill. As she stands there, unable to kill him, his heart begins to beat, letting them both know that she is destined to be his Bride. Sebastian has been a vampire for about 200 years, has detested what he is the entire time, as he was changed against his will. Now that he has met his bride, he may be changing his mind.