Demon's Seduction (Unabridged‪)‬

Three hundred years ago, Darius Alexander was bitten by a demon and his soul was ripped from his body. But Darius didn't die or become a demon. An angel saved him and made him a Knight of White, an immortal demon hunter. Now Darius is known as The Destroyer, possessing the ability to kill with his magic.  

But Darius is also a threat to the other Knights as his power grows stronger. The demon bite tainted his soul and he will turn into a demon himself if he does not find his mate, the one woman who can bring him salvation. After centuries of hunting alone to protect others, Darius believes it is too late....  

Then a fellow Knight introduces Darius to Cathy Baker, a human with magical gifts of her own. Their connection is instant and fierce, but Cathy also brings troubling news: a deadly sorcerer has formed an alliance with the leader of The Darkland Beasts, a group of soulless demons intent on destruction. Only together can Darius and Cathy face this evil - if Darius will abandon his solitude and let Cathy give him the love he needs to become a true Knight of White.