The Opposite of a Horcrux

[Chys Lattes]

No: HPFGUIDX 139264

What is the opposite of a horcrux?

I think that's the significance of Lily's sacrifice in her love for 
Harry, and his special eyes. Laugh at me if I'm wrong.

Well, anyway, a horcrux is where you kill someone to extend your own 
life. The opposite, couldn't it be, to give yourself up to extend the 
life of another? 

In one case your soul is split with the death being taken and in the 
other perhaps some bit of your soul is added to the protected soul? 
(Just a wild idea I added as an afterthought, but I do wonder if Harry 
was born with Lily's eyes or if it's the transformation that I believe 
is associated with a horcrux; LV's being the opposite- his becoming 
more like an animal and less human looking.)

Since a horcrux is something that's taboo and all of that, wouldn't 
the opposite of it be the same, as it's a similar principle? I don't 
think either idea would be a topic of conversation at Hogwarts anyway, 
as one would naturally lead into the other being associated with 
opposites and that could be why it's something that LV didn't know 
about.

Just wondering. I know for fact others have probably thought those 
same lines as we're all going nuts racking our brains for the answers, 
so if you have, that's awesome.

Chys, thinking too much and rereading HBP for a different take.