The Shadow of Orcus
Once a mortal who possessed great strength and power over death. It was claimed that she was the mortal consort of the god of death Nerull. During the battle with Orcus she threw him and herself into one of the portals to the Shadow continent. After that the portal instantly crumbled into rubble. There was never any account of the Raven Queen since that day but many believed that she had ascended to godhood and began worshiping her as one thus formed the clergy of the Raven Queen.