"Huh." Amber pulls a face at the old borg component. "That's what you all say!"

As soon as Amber steps onto the grass, she can feel possibilities open up around her. She has management authority here, and this universe is big , wide open, not like Sadeq's existential trap. A twitch of a sub-process reasserts her self-image, back to short hair and comfortable clothing. Another twitch brings up a whole load of useful diagnostics. Amber has a nasty feeling that she's running in a compatibility sandbox here – there are signs that her access to the simulation system's control interface is very much via proxy – but at least she's got it.

"Wow! Back in the real world at last!" She can hardly contain her excitement, even forgetting to be pissed at Sadeq for thinking she was just an actor in his Cartesian theatre's performance of Puritan Hell. "Look! It's the DMZ!"

They're standing on a grassy knoll overlooking a gleaming Mediterranean city. It snoozes beneath a Mandelbrot-fuzzy not-sun that hangs at the center of a hyperbolic landscape, which dwindles into a blue yonder that seems incomprehensibly distant. Circular baby-blue wells open in the walls of the world at regular intervals, connecting to other parts of the manifold. "How big is it, ghost? In planetary simulation-equivalents."

"This demilitarized zone is an embedded reality, funneling all transfers between the local star system's router and the civilization that built it. It uses on the order of a thousandth of the capacity of the Matrioshka brain it is part of, although the runaway excursion currently in force has absorbed most of that. Matrioshka brain, you are familiar with the concept?" The ghost sounds fussily pedantic.

Sadeq shakes his head. Amber glances at him, askance. "Take all the planets in a star system and dismantle them," she explains. "Turn them into dust – structured nanocomp, powered by heat exchangers, spread in concentric orbits around the central star. The inner orbitals run close to the melting point of iron, the outer ones are cold as liquid nitrogen, and each layer runs off the waste heat of the next shell in. It's like a Russian doll made out of Dyson spheres, shell enclosing shell enclosing shell, but it's not designed to support human life. It's computronium, matter optimized at the atomic level to support computing, and they're all running uploads – Dad figured our own solar system could support, uh, about a hundred billion times as many inhabitants as Earth. At a conservative estimate. As uploads, living in simulation space. If you first dismantle all the planets and use the resulting materials to build a Matrioshka brain."

"Ah." Sadeq nods thoughtfully. "Is that your definition, too?" he asks, glancing up at the glowing point the ghost uses to localize its presence.

"Substantially," it says, almost grudgingly.

"Substantially?" Amber glances around. A billion worlds to explore , she thinks dizzily. And that's just the firewall? She feels obscurely cheated: You need to be vaster than human just to count the digits in the big numbers at play here, but there's nothing fundamentally incomprehensible about it. This is the sort of civilization Dad said she could expect to live in, within her meatbody life expectancy. Dad and his drinking buddies, singing, "Dismantle the Moon! Melt down Mars!" in a castle outside Prague as they waited for the results of a shamelessly gerrymandered election to arrive in the third decade of the third millennium. The Space and Freedom Party taking over the EU, and cranking up to escape velocity. But this is supposed to be kiloparsecs from home, ancient alien civilizations and all that! Where's the exotic superscience? What about the neuron stars, strange matter suns structured for computing at nucleonic, rather than electronic, speeds? I have a bad feeling about this , she thinks, spawning a copy of herself to set up a private channel to Sadeq. It 's not advanced enough. Do you suppose these guys could be like the Wunch? Parasites or barbarians hitching a ride in the machine?

You believe it's lying to us? Sadeq sends back.

"Hmm." Amber sets off downslope toward the piazza below, at the heart of the fake town. "It looks a bit too human to me."

"Human," echoes Sadeq, a curious wistfulness in his voice. "Did you not say humans are extinct?"

"Your species is obsolete," the ghost comments smugly. "Inappropriately adapted to artificial realities. Poorly optimized circuitry, excessively complex low-bandwidth sensors, messily global variables —"

"Yeah, yeah, I get the picture," says Amber, turning her attention to the town. "So why do you think we can deal with this alien god you've got a problem with?"

"It asked for you," says the ghost, narrowing from an ellipse to a line, then shrinking to a dimensionless point of brilliance. "And now it's coming. We-I not willing to risk exposure. Call us-me when you have slain the dragon. Goodbye."

"Oh shit —" Amber spins round. But she and Sadeq are alone beneath the hot sunlight from above. The piazza, like the one in the Nursery Republic, is charmingly rustic – but there's nobody home, nothing but ornate cast-iron furniture basking beneath the noon-bright sun, a table with a parasol over it, and something furry lying sprawled in a patch of sunlight beside it.

"We appear to be alone for now," says Sadeq. He smiles crookedly, then nods at the table. "Maybe we should wait for our host to arrive?"

"Our host." Amber peers around. "The ghost is kind of frightened of this alien. I wonder why?"

"It asked for us." Sadeq heads toward the table, pulls out a chair, and sits down carefully. "That could be very good news – or very bad."

"Hmm." Amber finishes her survey, sees no sign of life. For lack of any better ideas, she ambles over to the table and sits down on the other side of it from Sadeq. He looks slightly nervous beneath her inspection, but maybe it's just embarrassment about having seen her in her underwear. If I had an afterlife like that, I'd be embarrassed about it, too, Amber thinks to herself.

"Hey, you nearly tripped over —" Sadeq freezes, peering at something close to Amber's left foot. He looks puzzled for a moment, then smiles broadly. "What are you doing here?" he asks her blind spot.

"What are you talking to?" she asks, startled.

He's talking to me, dummy , says something tantalizingly familiar from her blind spot. So the fuckwits are trying to use you to dislodge me, hmm? That's not exactly clever.

"Who —" Amber squints at the flagstone, spawns a bunch of ghosts who tear hurriedly at her reality modification ackles. Nothing seems to shift the blindness. "Are you the alien?"

"What else could I be?" the blind spot asks with heavy irony. "No, I'm your father's pet cat. Listen, do you want to get out of here?"

"Uh." Amber rubs her eyes. "I can't see you, whatever you are," she says politely. "Do I know you?" She's got a strange sense that she does know the blind spot, that it's really important, and she's missing something intimate to her own sense of identity, but what it might be she can't tell.

"Yeah, kid." There's a note of world-weary amusement in the not-voice coming from the hazy patch on the ground. "They've hacked you but good, both of you. Let me in, and I'll fix it."

"No!" Exclaims Amber, a second ahead of Sadeq, who looks at her oddly. "Are you really an invader?"

The blind spot sighs. "I'm as much an invader as you are, remember? I came here with you. Difference is, I'm not going to let some stupid corporate ghost use me as fungible currency."

"Fungible —" Sadeq stops. "I remember you," he says slowly, with an expression of absolute, utter surprise on his face. "What do you mean?"