Vampirism and Agency

So I was reading Brandon Sanderson's Elantris all week, and while it has nothing to do with Vampires, it brought up an interesting idea. So one of the groups of people in the novel have an affliciton which stops their hearts, lungs, etc. It's a very functional approach: they only need air to talk, limbs to move, etc. Food isn't necessary, but they still have a hunger. Anyway, the characters are very hard to kill, though their bodies never heal (and so pain is a big problem). As with vampires, there's only two ways to kill them: beheading and fire. Same with vampires, which is where I think I got this connection. In most vampire mythos, both are the best ways to kill a vampire. Steaking and garlic depend more closely on the story.

Anyway I was thinking about why this is. You have an immortal body, you don't need air or food. It's mostly understood that most of our body is simply in service of our minds (or at least, it's a common assumption, from what I know). So what happens if you behead someone who doesn't need their body? They can't do anything. Talking requires lungs. At best, they could move their eyes. Same with burning, without a body you remove a minds agency. Even if the consciousness can survive without a brain (it's unclear, there's only weak evidence), without a body, all it can do is ponder, and despair.

Of course, the point of all this in the Novel is to establish the necessity of Hope, and in some way Vampires work the same way. Hope is what keeps them from turning into beasts. Maybe there's something to be said for being an agentless being.