Sable lived for over a hundred years in the Shadowfell before the Raven Queen sent her to the Material Plane on a mission. This mission led her to an isolated community of people, where she was to work as an apothecary. After gaining the respect of the community, she began her duty. She would heal those who needed healing, but for those chosen by her queen, she would carefully draw their life force away until their soul was released into the Shadowfell, claiming that her potions and cures did not work on them.
And thus was the cycle of life and death. For over a hundred years, Sable would spare those who were not ready, and purge others from this world who would better serve her queen in the next.
One day, something terrible happens to the community, killing nearly everyone, and Sable believes it was foretold by the Raven Queen, and that she was placed there because of this eventuality. She learns at this time to enter her Quickening, and she sees into the Ethereal Plane and witnesses the tormented spirits left behind. Through her queen's guidance, she learns to bind those spirits to herself, drawing on their powers for a time until she chooses to release them and transfer their souls to the Shadowfell, where they can join the Raven Queen.
Finally, she has gained powers strong enough not to necessitate taking lives to help her queen. Instead, she can find those already dead, trapped within this world, and pass them along. With this, she gained some independence and was allowed to travel the world as she saw fit, so Sable joined the Orion Adventurer's Guild to find quests that would take her all over the land, and perhaps even the planes beyond.