My Heart is Within You - Triquetra Trilogy New edition

The power of heart and soul holds the key to the survival of the last of the ancient vampires. Kristair is running out of time. His race has faded away, prey to delusion and deterioration, and his only chance to live long enough to find a cure is to bind his psyche to a human vessel in a long forgotten ritual. Kristair's chosen vessel is Jacob Corvin, a man of passionate stubbornness and fierce loyalty; he has captured Kristair's fantasies so completely that he is both the vampire's greatest strength and most crippling weakness. Drawing upon Jacob's spirit and Kristair's resolve, they each bind a portion of their souls to one other. For as long as Jacob carries Kristair's heart within him, the vampire can continue his quest. Just when they have hope, their mission is threatened by The Syndicate, a group of younger vampires who attempt to force Kristair to teach them his secrets before he disappears like the rest of the ancients. Battling both The Syndicate's attacks and his unexpected need and love for Jacob, Kristair's strength begins to fade, forcing him to make a decision that will change his and Jacob's lives forever.