When talking about The Raven, in singular form, we are talking probably about THAT particular raven; the trickster who, tired of stumbling with things in the dark, allegedly stole the sun, the moon and the stars from the hoard of a troll king. Since then, the world was called the Daylands in his honor, and the title has passed along his bloodline.
Like him, all this raven chiefs have the power to shapeshift into a human; male or female depending on the raven's gender, but always dark haired and uncannily handsome and charming. And, as their liege subjects, they're fascinated with shining, glimmering things.
When your character dies and there is no turn of the page, a raven will come to take your soul and guide it to where the birds go in the winter (which is just another name for the land of the dead), on the other side of the world.
But if you roll a d20, and you get your level or lowest, it means that the ravens have told the current Raven Suzerain about your deeds, and he/she was so impressed as to come personally and resurrect you; against the natural order. Maybe s/he loves to hear about your tales, or has fallen in love with you. Maybe s/he just wants to ask you an important mission that only you will be able to handle (killing a wizard who has cheated death, or recover a shining thing at the bottom of a lake).
BTW I just learned today the word Suzerain, and I liked the ring of it!