Jack once was a demon who had lived for thousands of years. But a powerful magic user turned him human, and he has had to learn how to survive as what he thought of as "frail mortals."

Since then, he has become the adopted brother of Tiernan Barimen (who's last name you'll recognize if you are familiar with Amber Diceless) and has become comfortable as a human... after having some magical adjustments made (like getting a pair of wings).