The AK itself, Harry not a Horcrux

[raie8]

No: HPFGUIDX 140243

First time posting here, so ignore me if this path has been 
thoroughly trodden, but I have not read anyone mention what 
Moody/crouch told the DADA class during his demonstration of the 
unforgivable curses. He said that the AK requires the caster to 
use/give a part of himself to make it lethal. He went further to say 
that they could all point their wands at each other and say the words 
but nothing would happen because of what is involved in the process. 
IMO, LV `s attempt to AK Harry was repelled by lilly's protection, 
and due to the intimate involvement required by the caster in order 
to perform the curse, a piece or essence if you will, of LV was 
absorbed by Harry before the total impediance of all that energy 
combusted the caster.

My (half baked) interpretation is that the AK is using your own life 
force to overcome and disrupt that of another. It makes sense with 
what was said about the status of the victims and what Moody/Crouch 
said is required to make the curse work. There is no mark of any kind 
or trace of what happened; only their surprised/scared expression. It 
would fit with having your life force sucked/forced out. And in order 
to do that to someone, you would need to use that part of yourself to 
accomplish it. You would have to focus your very essence on the task 
and directed at the target. It also explains why it can't be 
countered/blocked. Logic would follow that the only thing that could 
block the Ki (for lack of a better term) of someone wanting to harm 
you is the Ki of someone trying to protect you. 
Why has it not been done in the past? They only knew of directing 
their ki in a negative way, ie the curse, and no one has willingly 
and unnecessarily given their own life to protect/save another, that 
wasn't already in mortal peril and to be potent enough. A primal 
devotion of a mother for her young could very well do just that.

Similar to how the patronus is a manifestation of your happiest 
thoughts focused and projected. The AK is the manifestation of your 
very being directed out, thus giving up a part of yourself. I don't 
thing the AK is necessarily evil, just that it is so raw and 
powerful, that it cannot be controlled to do anything else by 
destroy/disrupt that connection which binds that soul to the physical 
flesh.

Half baked, my apologies, it was either type or burst.
Raie