What if Lockhart had used Obliviate on Riddle's diary?

Question

While reading the Chamber of Secrets for the first time, I thought I had guessed the ending before I got there - you have a character who is good at nothing but memory charms, and a villain who is said to literally be memories. I thought that Lockhart was going to completely destroy the diary with his specialty charm. But that didn't happen.

Looking back, things are probably more complicated than just that the diary is "made of memories" since it is also a horcrux.

What would have happened if Lockhart had used Obliviate on Riddle's diary though? Probably not completely destroyed, but maybe something? Or maybe nothing.

With further thought, there are other things this could potentially affect as well - what if Obliviate is cast on a pensieve, or on the strands of memory that are put into a pensieve?

Answer 1

Obliviate cannot destroy a Horcrux because Horcrux can be destroyed only my something which does not allow Horcrux to repair itself.

“It doesn’t have to be a basilisk fang,” said Hermione patiently. “It has to be something so destructive that the Horcrux can’t repair itself. Basilisk venom only has one antidote, and it’s incredibly rare—”

_{^{Harry Potter and the Deathly Hallows, Chapter 6, The Ghoul In Pajamas}}

Scientifically speaking brain stores all the memories but based on Harry Potter and the Chamber of Secrets, a soul has memories too.

I AM LORD VOLDEMORT

“You see?” he whispered. “It was a name I was already using at Hogwarts, to my most intimate friends only, of course. You think I was going to use my filthy Muggle father’s name forever? I, in whose veins runs the blood of Salazar Slytherin himself, through my mother’s side? I, keep the name of a foul, common Muggle, who abandoned me even before I was born, just because he found out his wife was a witch? No, Harry — I fashioned myself a new name, a name I knew wizards everywhere would one day fear to speak, when I had become the greatest sorcerer in the world!”

_{^{Harry Potter and the Chamber of Secrets, Chapter 17, The Heir of Slytherin}}

Through out the books memory charms are used on humans but not on other things. So it is hard to predict what would happen to Riddle's diary or pensieve. But you must remember memory charm does not delete (destroy) a memory, it kind of erases a memory but powerful wizards can break the spell.

He tortured her until he broke through the Memory Charm my father had placed upon her. She told him I had escaped from Azkaban. She told him my father kept me imprisoned to prevent me from seeking my master. And so my master knew that I was still his faithful servant - perhaps the most faithful of all.

_{^{Harry Potter and the Goblet of Fire, Chapter 35, Veritaserum}}

Now we know following things:

1. Horcrux can repair itself
2. Obliviate some how hides/erases the memory
3. Voldemort was a powerful wizard who can break memory charms

Even if the spell worked on Horcrux, Horcrux would be able to recover from it and regain memory.

As for pensieve I cannot hazard a guess.

Answer 2

Given all of the spells used on the locket were useless, and only fiendfire worked on the diadem I would say we have to assume that the Horcrux in the diary would be too powerful for Obliviate.

It was destroyed by the basilisk tooth venom which also destroyed the locket.

There is nothing to suggest Obliviate would have any effect.

Answer 3

Pensieve is a tool to watch extracted memories, Obliviate seems to block the victim's access to their memory, not erase them. Thus it would have no effect on a pensieve.