Who is Death, from from The Sandman and what is their importance?

Death is a supernatural being like the Sandman. Where the Sandman's realm is the dream world, Death's realm is death. Whether a death is good or bad, Death is there. Death facilitates passage out of this world and on to somewhere else. Death appears to Rainie Blackwell as a comforter. Although at first Death says that she cannot interfere in Rainie's life and that it is not Rainie's time to die, Death shows Rainie how to achieve her goal of dying.