Angels Never Cry (Supernatural, DmC, Castlevania)

Dean receive a request from a mysterious woman, concerning a man named Dante, and a millennium old legend. She warns him that Dante had challenged a being too powerful, that it threatens the fabric of reality. Furthermore, a mysterious vampire with the powers equitable to a demon arises. Who are these mysteries? Why are they here? And can the Winchesters stop the end in time?