From the publisher:
Are your sins so hideous you know that when you finally die that you'll burn forever, and you would do anything to cheat God's judgment? Or do you love life so much, that you'll become something other than human in order to keep seeing new mornings, watching history unfold as an outsider? Or are the final sensations of death so ecstatic that you'll do anything to feel them again and again and again?
No matter your reasons, you've taken one step beyond: you've become an Unbound Soul, an immortal being that doesn't die like other men. The body you were born with isn't a vital part of you, it is merely a vehicle for your soul, which you can abandon in extremes, for convienience, or in seeking a moment's pleasure. Your restless, indestructible soul is bound to mortal life with your Psychopomp Cords, arcane ribbons, spiritual containment systems that tie you to this existence, and are the source of your cruel powers.