Where can I find a Crumble-Horned Snorkack? Not important right now.
Why is my mother a brain in a tank? Not important right now.
What is the countercurse to Fay's affliction? How to ask without ruining Fay's ambush?
"What happened to Chang'an?" said Luna.
Fay's ears perked up.
"I do not have all day," said the Unspeakable.
"What is the countercurse to your affliction?" said Luna.
"I am under the influence of the Fidelius Charm. Only the Secret Keeper can reveal my existence. I wonder who informed you of me," said Memnuela.
I wasn't informed of you.
"I thought the Fidelius Charm was immediately used in 683 CE to hide itself," said Luna.
"Writing is mind control. Don't believe everything you read. Time is up. Shall you join us?" said Memnuela.
"My mother. Did she make it this far?" said Luna.
"I offered you one question. No more," said Memnuela.
"I'll tell you who informed you of me if you answer my question," said Luna.
"You really are your mother's daughter. Your mother has done much of our best work on Space and Time. Would you like to see her again?" said Memnuela.
Luna's mother had traded her daughter for the secrets of the Universe.
Time out. Memnuela was pressuring Luna to make a quick decision under pressure. When someone pressures you into make a quick decision it's usually a sign that person is attempting to manipulate you into choosing against your best interests. Especially when such a decision supposedly involves lots of secrets.
What would happen if Luna declined? The Department of Mysteries would wipe her memory. Then what? Luna would rediscover the Department of Mysteries again. She would eventually find herself right back in the Department of Mysteries' Entrance Chamber.
What would really happen if Luna declined?
Magical Espionage: Theory and Practice was a honeypot. It contained misinformation. If a person or organization is willing to lie to you once that means they are willing to lie to you.
Memnuela had lied to Luna about the Fidelius Charm. The Secret Keeper couldn't counter the Fidelius Charm because the Secret Keeper revealing the secret of the Fidelius Charm was the Fidelius Charm working as intended. The Department of Mysteries did not know how to counter the Fidelius Charm.
"You can say no. We'll pretend this never happened," said the Unspeakable.
If the Department of Mysteries trusted Luna then why was Luna unarmed?
Luna's mother would never sell her daughter in exchange information she could deduce for herself.
What was Room Eleven for?
"You want to know who informed me of your existence?" said Luna, "CHANG'AN!"
Luna dropped to the ground as she shouted the last two words. Memnuela's hex shot where Luna's chest used to be and smashed into the brain tank, shattering it.
"Somnium!" Simultaneously, at Luna's signal, Fay cast a sleep charm at the Unspeakable.
The Unspeakable's armor blocked the child's sleep charm. A tentacled brain threw Luna her wand.
"Avada kedavra," said Fay.
"Trying to cast the Killing Curse in defense of another? That's adorable. Stupefy!" said the Unspeakable. Fay crumpled into a heap.
The floor was ankle-deep in green liquid. The tentacled brain launched itself at Memnuela. Memnuela was distracted. Luna would need a ridiculously overpowered spell to overcome the Unspeakable's armor in one shot. Ravenclaw's Diadem hadn't taught her anything that broken.
Memnuela tore the tentacled brain off of her face and threw it against the wall.
Luna's life flashed before her eyes. She recalled her first Potions lesson.
There is no Defense Against the Dark Arts teacher this year.
What happened to the third cauldron?
"FIDELIUS!" shouted Luna.