My impression was that LeBlanc died of his alcoholism.
I felt like there were some incongruities with Sylvain's character. He was such a manipulative and selfish jerk in the beginning and I didn't really see what happened over the course of the story to change him to how he was in the end. He was also extremely driven and proud, but seemed to have no sense of what his true goals or values were.
What I loved most about this story was the fatherly bond that developed between the nixie and Sylvain, culminating in the rescue from the fountain. The image of Sylvain cradling and rocking the nixie back to calm resonated with me as a father.
Rant warning.
Yeah, I think that is what the author was going for, but it didn't really work for me because Sylvain was the one who put her down there in the fountain in the first place. He captured her as a baby and forced her to work to gain his notoriety and favor from all of the terrible people in court. It makes me mad, like the videos of people "rescuing" animals from their fishing nets. It is good that Sylvain took her out of the fountain and had some change of heart, but that is the least he could do to maintain not-evil status. You don't become a hero when you are saving victims from something you purposefully did in the first place.