Your many trials against the vampires and their nefarious minions in D'Morte Burial Chambers, The Tombs of Night and The Crypt of T'haen have led you to this point. While undoubtedly the undead nature of vampires will cause trouble to rise again somewhere beneath that accursed cave under Soul Eater Falls, you and your closest allies have been tasked with this final quest by The Brethren of Night. Enter the Veiled Hollow, slay this renegade pack of vampires and learn of their intent.
Simply slay everything you see, and walk close to the three large sarcophagi strewn about the instance to spawn the named mobs. Once all the steps of the required quest are fulfilled, Ruenok G'Koz, the Rook Lord should spawn at his location in the middle of the instance. When he is killed it's safe to leave the instance.