Not My Canon!

WTF: Lily's Sacrifice

Whenever I speak with average Potter fans, there is always a glint of "huh?" in their expressions when it comes to understanding Lily's sacrificial protection over Harry. This ancient magic that starts out simply in Book 1 becomes more complex as the series progresses, culminating in a whopper of a reveal. It connects to the prophecy, to why Quirrell couldn't touch him, why Harry needed to sacrifice himself, and why it had to be Voldemort at the other end of the wand. This is extremely relevant to HARRY POTTER AND THE CURSED CHILD and, if you understand the nature of this magic, it paints a giant WTF on day two of your visit to the theater. Like, to the degree that someone should actually paint those letters on the building.

I'm down.

Sacrificial Death

Imagine yourself as Lily Potter. You were made aware that a prophecy was spoken about your son. A prophecy stating that he would overthrow the Dark Lord. You hide as best you can, through powerful magic and the trust of longtime friends. And then, after only a week in complete solitude, Voldemort casually enters your home and murders your husband. He moves toward your boy, your only child. And you know what to do. Maybe you've learned about this magic in the past, in the musty pages of some forgotten library book or during a boring lecture at Hogwarts... Maybe it's instinct. But you step in front of the spell and give your life for him, hoping that you can rest in peace with the knowledge of what might happen to your son after you die.

Lily Potter willingly sacrificed herself for Harry out of the purest form of love. And, by doing so, invoked an impossible magic that gave him the ability to defend himself against the might of his enemy. Not just in the ensuing moments of her death, but permanently. THIS IS EXTREMELY IMPORTANT TO REMEMBER. Voldemort, in any form, cannot harm Harry because of how Lily sacrificed her own life that cold October night.

The Horcrux and Scar

When Voldemort used the killing curse on this child, it reflected back onto himself, destroying his body and splitting his already fractured soul. This piece of Voldemort latched onto Harry's young soul, creating in him another Horcrux, a living Horcrux, albeit unintentional.

This portion of Voldemort impacted Harry in ways he wouldn't fully understand until later in life. Dumbledore even went so far as to call him a parasitic host.

"Part of Lord Voldemort lives inside Harry, and it is that which gives him the power of speech with snakes, and a connection with Lord Voldemort's mind that he has never understood. And while that fragment of soul, unmissed by Voldemort, remains attached to and protected by Harry, Lord Voldemort cannot die."

Lily's Blood

Where Voldemort went wrong was in using Harry's blood in the ritual at the end of Goblet of Fire to bring himself back to bodily form. This meant that, while part of Voldemort's soul resided in Harry, part of Harry's blood now resided in Voldemort. He believed this would give him the ability to kill Harry, since he wouldn't suffer the same fate as Quirrell. Unbeknownst to Voldemort, his decision to use Harry's blood augmented Lily's protection of him.

Voldemort's attempt was to nullify the protection, and the outcome was that as long as Lily's blood was still running through his own veins, it meant that he would not be able to kill Harry. He became an unwilling anchor for Harry's soul, functioning as a pseudo-Horcrux. Simply put, while Voldemort lived, Harry could not die.

Or could he?

The Prophecy

Professor Trelawney's prophecy stated that Voldemort would need to defeat the boy born on July the 31st. A boy whose parents thrice defied him. This prophecy was not widely known. Voldemort didn't have the specifics, which is why he wanted to retrieve the prophecy in Book 5. But he at least knew the part about "either must die at the hand of the other", which led him to conclude that, as long as he was alive, nobody else would be able to kill Harry Potter.