"What do you mean, 'made a place' for it?" Cohen frowned.
The brain was, without a doubt, talking about a Dementor. To these peculiar creatures, Cohen looked a lot like a Dementor himself, since he was sixty percent Dementor, after all. The Ministry must have captured a Dementor and put it into the brains' tank, hoping the brains would simply devour it.
"Just... made a place," the brain communicated back. It sent Cohen a feeling that was truly like setting aside an empty spot inside itself for new "thoughts" to join in.
"Can it leave?" Cohen asked.
"Thoughts can't be stopped," the brain replied. "It likes us, so it stays. When it doesn't, it will leave."
Then, the brain gave off a wave of pure happiness. Cohen siphoned it up, and just like human happiness, it was sweet.
Suddenly, Cohen understood why the Dementor "liked" these brains so much. It was a buffet! A voluntary, all-you-can-eat buffet!
The Dementor had joined them so it could feast to its heart's content. No wonder the wizards in the Department of Mysteries thought the brains could harm a Dementor; when a Dementor seemed to be sucked into a brain right before their eyes, it definitely looked like the brain "ate" it.
Unfortunately, the Department of Mysteries didn't have a "communication specialist" like Cohen who could understand the piercing thoughts the brains emitted. And there was a clear difference between humans and Dementors: a human's soul can't leave its body for too long, while a Dementor is a spiritual entity to begin with. So, what was a deadly hazard to a person was simply an open-door room for a Dementor. A room full of snacks, no less.
"Give me some more," Cohen told the brain.
"Okay," the brain replied, emitting another burst of happy thoughts.
This little snack was really useful. Since the brain was willing to offer up treats, Cohen not only changed its water but also moved it to a larger tank—the very one Lupin used to keep a Grindylow in. When Lupin left, it was thrown in the storage room, but Cohen had brought it back, thinking he might keep some aquatic animals someday.
With fresh water and a bigger tank, the brain could now swim around freely, its thought-tendrils swaying in the water, giving it an easygoing, almost carefree look.
"Cohen! Professor Dumbledore is back! We just saw him—Merlin's beard, what is that thing?" Ron burst into the common room, speaking happily to Cohen, then he saw the thing Cohen was playing with in the large tank.
"Join us?" the brain asked when it noticed Ron.
"It's a brain, you can probably tell," Cohen said. "Someone's gift to me. It seems to be from the Department of Mysteries."
"It must be incredibly rare, then... why would a brain be on its own..." Ron said oddly. "Ugh—it's so disgusting—"
The brain was still spewing out colourful brain fluid, as if it thought this was the way to tempt Ron to join it.
"It's actually quite cute," Cohen said. "Look, it can even swim—now turn over."
"Turn over."
Upon hearing Cohen's request, the brain flipped over in the water and then sucked its colourful brain fluid back in. It was a good attempt at playing hard to get, but it was sorely lacking in common sense. A normal person would not be drawn to a brain spewing fluid in a tank, even if the fluid was made of colourful thoughts.
"Ugh," Ron said, looking queasy. "You're not going to keep it in the common room, are you? It's gross. Professor McGonagall would never allow it."
"Of course not. It's a bit dangerous for you all," Cohen said. "It wants to pull people's thoughts into its own body—then you'd be stuck living in the same brain as it."
Ron shivered and took a step back.
"Did you say Dumbledore is back?" Cohen asked, covering the tank with a cloth, then preparing to stuff it into his Mokeskin pouch.
"Yes, Harry and Hermione went to see him. They should be back soon," Ron said. "But who sent you this 'brain'? It's dangerous for people... sounds like an attempt on your life..."
"It was definitely intended as a murder attempt," Cohen said, raising an eyebrow. "But clearly, they didn't succeed. I got a new pet and a future big project: I'm going to raise lots and lots of brains."
Then the Dementors could abandon their worldly desires and join Cohen to build a brainy society. He had the Department of Mysteries to thank for the generous sponsorship.
"You're in the same league as Hagrid now," Ron said, swallowing hard, only sitting down on an armchair once Cohen had put the tank away. "Of course, I mean when it comes to keeping magical creatures..."
Not long after, Harry and Hermione returned. Dumbledore didn't seem to have talked with them for very long, and Harry didn't look like he was in a better mood.
"What happened, mate?" Ron asked, puzzled by Harry's gloomy expression. "Dumbledore didn't believe you, did he?"
"Quite the opposite," Harry said, forcing a weak smile. "He believed us and even gave us a solution."
"That's great, then," Ron said.
"I'm guessing you have to learn some extra lessons," Cohen said.
"I have to take Occlumency lessons with Snape," Harry said, his smile looking less like a smile than ever.
"It's the safest way, Harry," Hermione said patiently. "You have to sever this connection. Dumbledore is right, it's dangerous for you and for everyone else."
"I'm not going to ambush you in my sleep," Harry said impatiently. "And I do want to sever the connection—but Snape... you know what he's like. He'll never teach me."
"He will, though. Remember, he's in the Order of the Phoenix, too," Hermione said.
"He looks like a spy to me; he's a Death Eater, after all," Harry said angrily. "He'll probably just torture me in his office instead of teaching me anything."
"Cheer up. You're just possibly going to be murdered. I've already been murdered," Cohen said comfortingly. "Someone tucked a brain into a bunch of gifts today, hoping it would swallow me whole."
"Tucked a... what?" Harry thought he hadn't heard the word correctly.
"A brain, a literal brain, the Ministry of Magic's big invention for fighting Dementors. It's my pet now," Cohen said. Suddenly, he patted his head. "Oh, right, I need to write to Edward quickly and tell him not to murder all those brains..."