Was it Harry's blood in Voldemort's body alone that allowed him to come back after dying in the forest, or the enchantment that it contained [duplicate]

Question

In Deathly Hallows, Dumbledore says:

He took your blood and rebuilt his living body with it! Your blood in his veins, Harry, Lily’s protection inside both of you! He tethered you to life while he lives!

So was it the fact that Voldemort used Harry's blood in Goblet of Fire that tethered Harry, or something about Lily's enchantment made it so Harry could use this connection to come back?

For example, if Lily's enchantment no longer was active and disappeared, would the blood connection alone be enough to bring Harry back? Or is it something about her enchantment that allowed him to use the connection to go back into his body and live? Is it because Lily's enchantment exists on Earth that Harry can come back, and the blood is just the host for the enchantment? So is it the blood, or the charm that it carries?

Does Lily's enchantment have that capability? If it is because the blood, how is the enchantment relevant. Dumbledore makes it sound like the charm does have something to do with his ability to return. Dumbledore made it confusing IMO by mentioning both, and not explaining how they correspond.

Answer 1

The enchantment it contained

“He took your blood believing it would strengthen him. He took into his body a tiny part of the enchantment your mother laid upon you when she died for you. His body keeps her sacrifice alive, and while that enchantment survives, so do you and so does Voldemort’s one last hope for himself.”

—Harry Potter and the Deathly Hallows

To address your points in order:

• If Lily's enchantment no longer was active, would the blood connection keep Harry alive?

  No. Without that, Voldemort has only taken taken someone's blood into himself, nothing more. Recall that the spell requires blood of the enemy:

  “B-blood of the enemy . . . forcibly taken . . . you will . . . resurrect your foe.”

  Harry could do nothing to prevent it, he was tied too tightly. . . . Squinting down, struggling hopelessly at the ropes binding him, he saw the shining silver dagger shaking in Wormtail’s remaining hand. He felt its point penetrate the crook of his right arm and blood seeping down the sleeve of his torn robes. Wormtail, still panting with pain, fumbled in his pocket for a glass vial and held it to Harry’s cut, so that a dribble of blood fell into it.

  —Harry Potter and the Goblet of Fire

  We know that the potion is ancient magic:

  “I knew that to achieve this — it is an old piece of Dark Magic, the potion that revived me tonight — I would need three powerful ingredients.

  —Harry Potter and the Goblet of Fire

  Given that the potion requires the maker to have their enemy's blood at their disposal, and that one of the first things a Dark Wizard might do upon returning from the dead is to attempt to kill their enemy, this makes it very unlikely that the potion normally will preserve the life of the one whose blood was used to create it.

  This is supported by Dumbledore's words, indicating that Voldemort "took into his body a tiny part of the enchantment," and "while that enchantment survives, so do you."

• Is it because Lily's enchantment exists on Earth?

  Not entirely. The enchantment existed within Harry still, and that alone would not have stopped Voldemort (as evidenced by the mention of the blood). It is basically because Lily's spell existed somewhere besides within Harry.

Answer 2

It was Lily’s enchantment, which was carried by Harry’s blood.

Lily’s enchantment being in the Dark Lord was what tethered Harry to life. Harry’s blood was only relevant because it carried this enchantment in it, so the Dark Lord using it to rebuild his body also means that along with Harry’s blood he’d have taken some of that enchantment.

“Without meaning to, as you now know, Lord Voldemort doubled the bond between you when he returned to a human form. A part of his soul was still attached to yours, and, thinking to strengthen himself, he took a part of your mother’s sacrifice into himself. If he could only have understood the precise and terrible power of that sacrifice, he would not, perhaps, have dared to touch your blood … but then, if he had been able to understand, he could not be Lord Voldemort, and might never have murdered at all.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 35 (King’s Cross)}}

The Dark Lord kept Lily’s enchantment alive within himself because he’d used Harry’s blood containing it, which tied Harry to life because Lily’s enchantment and its protective power over Harry still survived in the Dark Lord’s body. J.K. Rowling explains this in the F.A.Q. of her website.

Having taken Harry’s blood into himself, Voldemort is keeping alive Lily’s protective power over Harry. So Voldemort himself acts almost like a Horcrux for Harry – except that the power of Lily’s sacrifice is a positive force that not only continues to tether Harry to life, but gives Voldemort himself one last chance (Dumbledore refers to this last hope in chapter 35). Voldemort has unwittingly put a few drops of goodness back inside himself; if he had repented, he could have been healed more deeply than anyone would have supposed. But, of course, he refused to feel remorse.
_{^{- F.A.Q. - What exactly happened when Voldemort used the Avada Kedavra curse on Harry in the forest? (J.K. Rowling’s website)}}

Since the Dark Lord kept a part of Lily’s enchantment alive even when Harry was hit by the Killing Curse, Harry was tied to life externally in a way similar to if he’d had a Horcrux. Dumbledore refers to this when talking to Harry in King’s Cross - it was Lily’s enchantment that kept him alive.

“He took into his body a tiny part of the enchantment your mother laid upon you when she died for you. His body keeps her sacrifice alive, and while that enchantment survives, so do you and so does Voldemort’s one last hope for himself.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 35 (King’s Cross)}}

The enchantment was the reason why Harry survived - if his blood didn’t carry the enchantment, he’d have died. If the Dark Lord had used the blood of another of his enemies, one whose mother didn’t die to save them, he would still be able to kill them despite having used their blood - just taking someone’s blood wouldn’t be enough to tether them to life.