I was just realizing that maybe the reason that there are no Volkihar vampires in Skyrim (although they are mentioned in the lore) is that they were driven out. By whom? Movarth Piquine. He is featured in the very book the Volkihar are mentioned in,http://www.uesp.net/wiki/Skyrim:Immortal_Blood. Movarth was a Fighter's Guild trainer who became a vampire hunter, mentored unknowingly by a Cyrodiil vampire. The vampires in Skyrim are literally identical to the vampires in Oblivion, so they must be the same type. This Cyrodiil vampire turned Movarth into a Cyrodiil vampire by biting him. *SKYRIM SPOILERS* In a quest in Skyrim, you are tasked to defeat Movarth Piquine and his clan of vampies in order to save Morthal. Since Movarth had so much experience in vampire hunting, he was probably able to drive the Volkihar out of Skyrim, and install the Cyrodiil vampires as the dominant vampire clan of Skyrim. Maybe the Volkihar will return in Dawnguard or another future DLC?