tragical endings and a question

[o.g.p.]

No: HPFGUIDX 85744

Hi everybody, I'm the new guy, so let me introduce myself. My name is 
Odil and I'm writing from Mexico.

Why isn't HP able to resist the effect of the touch of Voldemort?
Is this something to do with the scar or the protection of Lily's 
sacrifice? If so what kind of protection is that?

Imagine this ending:  

Sister wands = no damage between HP and LV, but what if HP is possessed by LV and then some kind of spell that compels both of them to stay together. Who is going to survive?

extreme_0210