It does take him a couple seconds of silence to realize that this is what's happening, but after a couple of seconds he moves back inside the barrier and sits down on the floor again. 

Then Dream can go back to hiding in the corner and having a very quiet panic attack!

The cell is a box, about 6x5x2, made of obsidian and crying obsidian. The only escape is lava. There is a cauldron full of water, a glowstone lamp, a one-block pool of water in the floor, and a double chest. The barrier is a row of solid black blocks of whatever the armor’s made of embedded in the floor that come up and down. If he checks what's in the double chest, the answer is a few empty books.

After a bit, not taking his eyes off Quackity, Dream inches back towards the lava. “Want to see a cool trick?”

He's not moving. He's staying right where he is, sitting on the floor, as nonthreatening as he can feasibly be under the circumstances. 

"...sure." 

Fun trick: Dream can touch the lava, flinch away, and then repeat this a few times!

Even more fun trick: Dream can kill himself in the lava and then appear again, totally uninjured, in the one-block water pool!

What the fuck!! 

"That’s— certainly a trick?" It comes out of his mouth kind of strangled but he does successfully make words happen! 

Nod. He touches the lava another few times, almost lazily, to demonstrate further. It’s easier than trying to figure out conversation topics and then make his mouth cooperate, it’s not boring, and Quackity’s reaction is interesting. Supports his story. 

After about a minute of this, Quackity-- who has been watching in increasing horror-- opens his mouth to say something about it, realizes he has nothing at all to say about it that is not horrible, realizes that it is really not his business and his whole deal here is premised on not acting like he wants to order Dream around, realizes he still hasn't said anything--

starts monologuing about the first non-personal topic he thinks of. Which is beekeeping. 

Dream comes away from the lava and goes back to cowering in the corner, wedged next to the chest. He doesn’t relax at all, stays coiled and ready to run, but he isn’t sticking his hand in lava anymore, just tucks it between his knees and listens to other-Quackity talk about beekeeping. He keeps startling and flinching at the voice, expecting it to turn at any second to a sharp edge cutting into him, but it doesn’t. Other-Quackity doesn’t draw his weapons. He decides it’s not as good as when Techno was here, but definitely better than being alone, and it’s also better than when Techno was here because he knows Techno will be helping get him out soon. Hopefully.  

He's careful about his tone of voice, keeps it chill and casual and slightly friendly but not, like, overly friendly, not so much that it sounds like he's doing customer service. He holds still. He doesn't approach Dream. 

At some point he runs out of things to say about bees, and moves on to the next non-personal topic that comes to mind, which is accounting. 

The things he says about both bees and accounting are absolutely outlandish. Dream's enraptured. 

Eventually: "Are you from Hypixel?"

"Nope! The place I'm from is called Panem. Nobody I've asked around here has ever heard of it and I have no idea how I got here. I haven't gotten a complete list of ways it's different but a lot of things sure seem to be." 

"I've never heard of that many people except on Hypixel."

He'd been in the middle of a tangent about business accounting but he doesn't think he's mentioned any specific numbers of people bigger than a couple hundred?

"...wait, how many people does the Dream SMP have?" 

"...Thirty-two as of when I was imprisoned? Plus DreamXD."

Thirty-two. Holy fucking shit. That's-- that's not even village numbers, that's apartment complex numbers. 

"...well, Panem's got a population of forty-five million," is what he says. "I think there's other countries but not near enough to us that I know their population off the top of my head. A couple hundred is, like-- a medium-sized business, maybe? A really small town?" 

"Hypixel's probably got a few hundred thousand? It'd be in the millions if you looked at how many people have ever lived there. It's, y'know, it's big. Most servers are, um, closer to the size of the Dream SMP."

Okay so he needs to reevaluate everything he thinks he knows about this place. 

He-- probably should not do that here. He is still, in fact, being watched; anywhere else, that was a guess, but here it's a certainty.

"A few hundred thousand people in a world being big is a little bit wild to me but if you've got thirty-two I can see how it would be. Holy shit." 

Dream moves as he talks; he's still not turning away from Quackity, but he's not as deathly still as he had been. "The place I'm from was bigger than this, smaller than Hypixel. Somewhere around a million people have been there? Probably tens of thousands lived there, not hundreds. Other big servers do exist. But Hypixel's the biggest."

So servers are the kind of thing you can move between, and that's unexceptional-- nope, stop it, reevaluating is for Not Here. 

He does know enough about his country's demographics, district population breakdowns, population centers and their sizes, and so on to have an intelligent conversation about them! He's still careful with his voice, both tone and volume, but he does get slightly more animated; he stays seated on the floor, shifting positions when his legs start to protest. 

Dream will talk about things—not about anything that might help Quackity, nothing about the recent history of the server, but safe things like Punz’s bees and Tubbo’s bees and the population of munchymc vs hypixel vs SMP Earth and trying to discreetly figure out what money is—and gradually relax. Not to the point of actually not tensing everything, but to the point where he’ll warily pace the room while keeping his eyes fixed on Quackity. If Quackity tries to leave, he’ll pull the same stunt, standing right next to him until he either gives up or forces him back; if Quackity asks, he’ll openly threaten to continue doing this.

He doesn’t sleep, the first night; doesn’t even get too tired. Just stares at Quackity, trying to guess the content of his dreams.

(If Quackity stays, he doesn’t sleep the second night, either, or the third, or the fourth. He’s started self-harming with the lava again, whenever he nods off.)

Quackity can pull one all-nighter, if he's got someone to talk to the whole time; he cannot pull two. Or, sometimes he can, but he didn't bring caffeine with him, and also he shouldn't. 

"--If I solemnly swear that I intend to come back, will you cooperate with me leaving," he finally says, at some point in the morning of the second day. 

“Sapnap said he’d come back. And that he’d get George to visit. And BadBoyHalo said he’d come back. And Ranboo said he’d come back.”

"...okay, that makes a lot of sense, but I cannot actually stay here forever and I would really prefer not to hurt you about it." 

Dream rolls his eyes. “You can leave if we run out of food.” (Sam hasn’t been dropping enough for two, just the usual rations of raw potatoes.)

(Dude, why the fuck would you say that where Sam can hear you.)

"Okay, no, seriously, let me leave." He stands up, stands on the outside of the barrier.

He doesn't want to use the sword and he sure fucking hopes he won't have to choose between that or starvation but-- he's holding it.