This fantasy novel that I have been trying to find for the last twenty five years was responsible for turning me onto the fantasy genre in the first place. I desperately want to revisit this book again, as I read it as a wee boy. I don't remember the story too well, but I have always remembered the lasting impression that it gave me. I hope you can help.
This particular fantasy novel was probably written between 1970 to 1990. It's not for kids by any means as it contains gratuitous violence, and sex and it's written so eloquently.
The story takes place in a conventional fantasy realm and centers on a few special young humans (male and female) that are imbued with extraordinary magical gifts. These special individuals are marked by having magical gemstones embedded in various parts of their body. For example, one guy has a red gemstone implanted in his forehead. Another has a sapphire gemstone implanted in the center of her palm. A blue gemstone in the chest, etc.
There's an evil malevolent female character who is trying to track them down and harvest their gemstones for her personal gain. On the outside, this evil female looks and acts like an aristocrat, but her true form is something of a slithery demon with a forked tongue. I remember she uses sexual seduction to trick and murder one of these special humans.
I realize that these are the barest and vaguest of plot details, but that's all I can recall from when I was twelve years old. These gemstone-implanted people are also featured on the book's cover.