By your definition then Kain could be a bodyless entity that uses Telekinesis and so forth to operate like some other specters. But that isn't the case for Kain, clearly.
What I'm saying is, he needs so sustain himself by some means. Not constantly needing blood ,but time to time. A heart isn't always needed for some beings to live. A heart is only an organ to help circulate blood, but if Kain has a manipulation over blood, I don't see how a heart would serve him. With or with out it, it is void. He already can pump and circulate his own blood.
Blood is needed to circulate and move nutrients and oxygen, oxygen playing a huge roll in body movement and exercise.
What I'm getting at is, Kain has blood in him, correct? He needs that blood in him at least, because blood is used to give oxygen.
Vampires are only evolved homo sapiens. Higher intellect, strength, agility and other things. The only thing, they don't seem to need to breathe air for oxygen. Like a fish. They instead get oxygen by means of when feeding from the blood of others. And they normally do need blood. eventually. Even if it isn't a constant feed. And I stated a heart is useless to some one like Kain who seems to have this power to manipulate Blood. So ....Kain does need oxygen e.g. blood to live and sustain himself, even it is minimal.
I'm not trying to ask you this to get information how to beat Kain by the way, but because Kain is such a highly developed species of Vampire, I wanted to see your view of that.