User blog comment:Zippertrain85/Vampires are NOT undead in TES/@comment-7813150-20140731000323/@comment-6336669-20140731011218

The fact that magic needs to be changed but not alchemical potions might have something to do with my theory that Vampires don't have dead bodies, but their souls have already been transferred or partially trapped by Molag Bal. I'm replaying the game at the momwnt, and I just got to the part in Dawnguard where you enter the Soul Cairn. Serana doesn't explicitly say she's undead (Maybe she does if you choose to become a Vampire) but she *is* immune to the Soul Cairn's effects. Which means she, and all vampires, have their souls already claimed by Molag, taking it away from the Ideal Masters, while the player's hasn't officially been totally "claimed" by anything, from Daedra to Divine, making it ao you need to become partially soul trapped, giving a piece to them.