“Arcanists have debated the nature of the… curse? For literal ages,” Elspeth will reply, warming to the topic of Dainan is not unduly upset. “Being that the origin of vampirism is literally a magical curse, I am of the opinion that the blood dependence is magical in nature.” The veins throb beneath Dainan’s thin skin. The blood rushes. It’s a song that calls to Elspeth. It’s an intoxicating odor. She swallows back the red thirst. “Elves here… uh… would work. I don’t know if that is because you’re sufficiently sentient, or because you are sufficiently similar to elves where I came from? Lizard men and greenskins- orcs and goblins- were sentient- certainly more so than animals- but their blood was not more nourishing. In the case of orcs and goblins it could even often be more harmful, but that was I think more the pollutants in the bloodstream than the blood itself.” 

Elspeth will not respond to unspoken concerns about continuity of self even though she remembers her childhood quite clearly and does in fact feel like the same girl. 

Dainan is oblivious to the fact that she is breathing, and circulating blood, and producing scents, and other such activities. Or at least, oblivious to its salience.

"So it might be possible for blood to have the useful property but to be harmful anyway? I want to look for the prevailing principle, but I doubt I have a special advantage beyond your ability to reveal it."

“There have been a large number of studies into the nature of vampirism, often with horrific moral implications. The nearest anyone can guess is that it’s transactional in some bizarre baroquely magical way. Just as one draws from fire to create a fireball, the vampire draws vitality in some way to continue their eternal vigor? Nothing seems to be taken from the… donor…” don’t say victim “except the blood though. There have hardly been controlled studies, because most possible studies are grossly unethical, but… My preference is to only take from a small pool of consenting donors.” Don’t think of countess Emmanuel… don’t think of the taste of her sweet blood or the feel of her silken sheets, or the scent of her warm body… “Um. Those donors have not had noticeably shorter lives, and elven donors have remained ageless…” 

"If the donor isn't magically affected, then is the blood mostly symbolic, or triggering of a different process? I've heard of types of natural magic that require a local trigger but that doesn't draw on the trigger for the energy. Oh, wait, what are the horrifying implications of studies? Does Nuln do a lot of studies? Do a lot of them have moral implications?"

“I have legitimately no idea whether it is symbolic or otherwise. Certainly there is an associated hunger which closely matches what I recall of mortal hunger for food back… er, before… Um. Nuln did many studies but not in as careful or scientific of a manner as would be preferred. Um. Most of their studies were not horrifying. How much pressure can this boiler take before it explodes, while everyone stands a few hundred feet away, for example. Um. Checking what quantity of blood loss has adverse effects on donors is a… complicated sort of study to do in a moral manner, and those attempting such studies rarely had any desire to keep their studies moral.” That’s… certainly one way to describe Tsarina Kattarine’s penchant for bathing in the blood of virgins… “I would stress that I have never participated in that sort of study.” 

"Complicated how? I'd think that with the risks so obvious and specific, they'd be easy to price? It's hard to be uninformed about the affects of blood draining."

“That’s an interesting- and probably effective- way to handle… scientific studies. I… don’t get the sense anyone was particularly concerned with paying their test subjects.” 

"That...doesn't sound very sustainable? In any of the ways I could see that working."

“It wasn’t. Which, of course, meant that such studies were rarely attempted, as mentioned.” 

"Oh. I guess that makes sense."