It is rumored that The Raven Queen was once a powerful mortal sorcerer-queen and that after death she somehow managed to steal Nerull's power over mortal shades, and to somehow destroy Nerull and become the new god of death.
After overthrowing Nerull, she erased her true name from the knowledge of all creatures then abandoned the land of the dead and created her own realm known as The Nightshade Kingdom. From there she rules over the dead as well as the forsaken of Corellon, known as the Shadar-Kai.
She is enigmatic and elusive, but she can be glimpsed atop her tower in the Shadowfell known as The Fortress of Memories