Sorry for the vagueness of the following description but I can only remember some of the info on the book, my high school days were a blur.
The series was set in a somewhat Renaissance type period where some characters had the ability to drain powers/life from others. The Church of the time was against it and they had to keep hidden. One of the main characters I remember was missing a hand and would push his stump against people when he pulled their power.
It was a multi-book series and I only started on the first book before I got distracted (was easy in those days!) and had to take it back to the library. I think at that time I found the Pern series and got totally distracted with them and never picked it back up again.