Dumbledore wonders if one of the remaining two Horcruxes belonged to Ravenclaw, since Gryffindor's only known relic, the sword, is safe in Dumbledore's office. Dumbledore believes that Nagini, the snake, is the sixth.
Dumbledore also theorised that he believed Voldemort made his snake Nagini a Horcrux. Dumbledore also speculated that Voldemort was one Horcrux short before entering Harry's parents' house with the intention of killing Harry.
Dumbledore gets confirmation that Voldemort did indeed make a Horcrux, but alarm bells go off in his head. If Voldemort treated his Horcrux as expendable, that means that Voldemort must have made more than one. This is a mind-blowing idea, but it appears to make sense.
Dumbledore starts painstakingly collecting or reviewing old memories—from Bob Ogden, Morfin Gaunt, Horace Slughorn, Hokey, and probably many others—to discover what the other Horcrux could be. As Dumbledore realizes that there are multiple objects that could have become Horcruxes, he develops his 6-Horcrux theory.
Dumbledore knew it meant Harry would need to die in order for Voldemort to truly die, so he was pleased to know that Voldemort's mistake in taking Harry's blood might just save Harry's life. DUMBLEDORE: [Voldemort's] body keeps her sacrifice alive, and while that enchantment survives, so do you . . .
Voldemort can not comprehend love, and so it destroys him to touch Harry because Lily's love for her son runs through Harry's veins and body. ems Harry burnt Quirrell's face when he touched it.
Voldemort hugged Draco as an improvisation and it wasn't planned. Even Tom Felton (Draco Malfoy) was caught unaware which increased the effect. In Harry Potter style, it was like a welcome for Draco, but as Voldemort had never known love, he didn't know how to hug him very well. Thats why they had the awkward hug.
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
The Dark Lord — aka Voldemort — created seven Horcruxes in an attempt to sustain immortality. But, as you may have heard, Voldemort's plan ultimately failed. Harry Potter and co. found and destroyed all of his Horcruxes.
A Horcrux is considered destroyed when it's damaged beyond repair. In the case of living Horcruxes, “damaged beyond repair” would mean dead. So, yes, Avada Kedavra can destroy a Horcrux, as long as that Horcrux is a living being.
First of all, Dumbledore didn't reveal the secret of horcruxes to Snape because he didn't find it necessary. It wasn't his style to let out unnecessary secrets to people. Making horcruxes to fight horcruxes wasn't the plan.
Voldemort wasn't aware of Harry being a pseudo-horcrux because he didn't plan it, and Harry didn't know either until Voldemort “killed” him, but he actually killed the piece of soul kept in him.
In the Harry Potter and the Deathly Hallows book, Dumbledore admits to Harry that he only offered him scarce clues towards Voldemort's demise because he was afraid that Harry's hot-headedness would overwhelm his good heart if he were to know everything too soon.
“Dumbledore didn't want to lose his wand at that point and Draco disarmed him. So that meant that the wand gave Draco its allegiance, even though Draco never knew it, even though Draco never touched it. “From that moment on, that wand gave its allegiance to Draco, and it wouldn't work as well for anyone but Draco.”
Voldemort fears Dumbledore because he knows Dumbledore is more powerful than him, having known Dumbledore and Grindelwald's duel in 1945, and he had just finished school that time. Voldemort feared suffering the same fate as Grindelwald.
Dumbledore believed that he knew what was best for everyone, whether it be using Snape's guilt and grief to turn him to the Light side or lying to Harry to protect him from knowledge of his fate. But he had no right to such condescension, no right to manipulate the lives of others, no matter how noble his purpose.
So when Ron said three, it wasn't a mistake. He meant there were three more horcruxes to destroy before being able to destroy the fourth and final piece which was in fact Voldemort himself.
Quirrell tried to put up feeble resistance on occasion, but Voldemort was far too strong for him. Quirrell is, in effect, turned into a temporary Horcrux by Voldemort. He is greatly depleted by the physical strain of fighting the far stronger, evil soul inside him.
The most likely reason why Lord Voldemort's nose disappeared and he devolved into such an evil-looking creature is that as he dabbled deeper into the Dark Arts, his appearance gradually became as distorted as what remained of his twisted soul.
Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Though Harry encountered many opportunities that deemed Avada Kedavra necessary, it remains as one of the Unforgivable Curses Harry Potter never cast. For one, he viewed the spell as an immoral practice commonly used by users of the Dark Arts.
Lily's Protection In Voldemort's Blood Saved Harry
When Lord Voldemort returned Harry Potter and the Goblet of Fire, he used Harry's blood - which is partially how Harry survived Avada Kedavra in the forest.
Narcissa's greatest moment, however, was when she chose to betray Voldemort in Harry Potter and the Deathly Hallows. Not knowing whether Draco was alive or dead, Narcissa chose to lie to the Dark Lord rather than risk losing her son.
Despite being a valued Death Eater in the days before Voldemort fell following his attack on baby Harry, Lucius stumbled out of favor with the Dark Lord when he squandered Riddle's diary (secretly a horcrux) in Chamber of Secrets and failed to obtain the prophecy in Order of the Phoenix.
Lucius Malfoy's failure at the Department of Mysteries combined with accidentally destroying part of Voldemort's soul with the diary of Tom Riddle resulted in his loss of any standing with the Dark Lord.