So Astarion is Faerun Angel?
Nope Astarion is a vampire like in the traditional european culture. The buffyverse stats that vampires are dead bodies possesed by a demon soul. (A big plothole is the reason why Angel has his human soul).
The fact that vampires have a soul doesn't imply they have to act moral. The fact that they are souls entrapped in a dead body by a curse twist and corrupt them (something beatiful managed by White Wolf: vampires have to struggle to mantain their humanity, and those who didn't believe in humanity have to follow their own moral codes, a failure in this would brought them more and more near a feral state in wich they are driven only by basic insticts).
Indeed a recurrent cliche in the vampire lore is the one with a vampire choosing an hign moral person to embrace in the vampirism.
A note that should have been in my previous post: nothing in the Raphael cut scene and dialogue implies a devil's deal with a soul as a price. Shadowheart simply states that a bargain with a demon cames with a price to pay but let open the possibilities of what could be that price that is for Astarion could be the loss of his chance to be free from his master, or the passage from one master to another, even in fairytales and fables not always the devil's deal requires a soul to be put on the plate, sometimes it is the daughters and sons that are the price, other times is to corrupt or to aid in the devil's projects.
The idea of the soul as a bargain coin I think comes from the tale of Dr. Faust, that is but one of many stories that involve a pact with the devil.
