Like any neoromance, a girl is surrounded by many men. The girl in question is Angelique. One of the many men is Nyx. While Nyx is well known and has plenty acquaintances, it would seem Angelique is the only woman in his line of vision.
While he has roamed Arcadia for two centuries, one can only guess whether he had ever entered a serious relationship before. One would also have to question if he’d even be willing to take such a chance. Based on what I have seen, he seems well versed in treating a woman well, but he only lets it go as far as that. Even when Angelique enters the picture he is about the same, but over time he is quite willing to tell her of his fondness and interest in her.
Upon their first meeting it was simply business and persuasion. While Nyx saw Angelique as a person, he also saw her as someone he had to win over no matter what, thus she was almost like a prize. While aware of her feelings, he was still a bit standoff and seemed to only care to get what he wanted. If you read the section The Armoire one might even say he was only out to use her.
Perhaps in the beginning he more or less was, but as they spent time together it is obvious he began to see her as more than a means to an end. Seeing her as his salvation can have negative and positive reasons, but the question is, did he feel for her because she was the only one who would be such to him, or did he really come to love her as Angelique alone?