These days I thought a lot at the real vilain in vampire knight.
We know that kaname tried to accomplish his original plan. however he hesitated countless time.
We do know he tried to create a better world for yuuki doing so, but we still don't know what triggered his decission to accomplish his plan now.
I do have the feeling Sara is not the real vilain here - of course I could be wrong, but we are here to theorize about it .
The first arc had two vilains: shizuka, and rido. About rido existence, the real vilain in the first arc we find out near the end.
In my opinion is too obvious for sara to be the real vilain. From the biggining she showed signs of her desire to conquer all.
Until now she made plans to create a small army. she turned human girls into vampires, she killed ouri, and took hana's heart. and she even created those blood tablets.
She had her own way to accomplish things, and to get things - like a hunter.
but in vampire society happened more than just sara's actions.
1. a child is kidnapped, and saved by zero
The first arc start with this. Zero asked the vampire who is his master, and the vampire refused to answer.
I doubt the master is sara, since she hadn't showed interest in small children.
2. another child is kidnapped, and saved by zero.
To me this sound like an premeditate act.
Could these kidnappings to show another pureblood we aren't aware yet, and to be the real vilain?
3. humans girls are sold at an auction.
I do doubt is about sara - she would have turned the girls into vampires, not sell them. Beside, if she would have been behind those auctions, which attracted hunters attention, she wouldn't have distributed her tablets near that area.
If the pattern of first arc would repeat, sara would die soon - my theory is that sara would die around chapters 80-84 - and the story would focus on another pureblood, the one who made kaname to fulfill his original plan.