The adventurers wake aboard their spaceship. Interior illumination winks and flickers. Then, outboard lights.The stale waft of century old air hangs for a moment before the life support system comes fully online. A greasy blur obscures the windows of the spaceship, veiling all vistas of the starfield outside.
Soon, the crew is fully revived. The ship's command module is unable to interpret sensor readings. Without star positioning data, the navigation computer cannot calculate a current location. Worse, the ship is completely immobile. Thrusters fail to pitch the ship forward--or in any direction. Instead a terrible shimmy rocks all aboard. A rumbling warble of steal echos.
It's not going anywhere for a long, long time.
Sensors finally begin to pick up shapes in fixed positions around the vessel. Some nearby, some many kilometers away. None of them exhibit the usual "drift" that derelict vessels or debris would indicate. If the ship is unmovable, then perhaps they can make their way to one of the many abandoned craft? Or...the thousands of satellites both natural and constructed ("That's odd," the captain thinks), or...ancient ruins?
Some sort of temple from a forgotten time seems to have been plucked from the ground--while still embedded in it's earthen bed. A massive kaiju skeleton lies wrought in opisthotonus. The silvery head of a massive Celestial One stares vacantly, still helmet clad. Space junk from every era of humanity's time amidst the stars, surrounds the assemblage of strange objects. The sensors can't be right--can they?
It's up to our heroes to find out. They embark on a daring escape, taking only what they--and a few robot companions--can carry, unaware of the perils to come or the danger that fills the space around them.
The party could spend months traveling from one stop to the next, oblivious that the volume that they, and the other detected objects occupy... are already consumed. They were prey while they slept in suspension aboard their spaceship.
Outside that oddly blurred window, the spread of debris in this particular patch of inky black night fits neatly into a 300 by 300 by 300 kilometer behemoth. A monster of unfathomably cosmic indifference and perpetually unsated appetite. It roams space on an endless quest for no other purpose but to feed. It is all at once a wandering monster and migratory megadungeon.
Eons old, it is the most feared predator in any galaxy, it is the...
And they must fight their way out.
This is a really bad illustration of how a GGSC might look. I'm no artist. Let me say that again: I'M NOT AN ARTIST. So this sucks. I'd hoped to make the objects look a little more convincing that they were floating in (and in some cases with parts both in and out of the cube) but we're at the edge of my abilities here, so--sorry! In any case, you get the idea....hopefully.
Everything inside the cube is in some sort of state of decay. The kaiju is likely in the roughest shape since it's organic. I expect that's the environment most dangerous to the players (cube jelly stuff leaking in and eating away at the innards, etc.).
I'd also wanted there to be a more obvious connection between the objects--like you could move from one to the other. I figure the biggest starship might even have a transporter/teleportation chamber so you could hop to any number of places. There's a few other pieces of debris though that could be used to grasp onto if the PCs had spacesuits (though those wouldn't last too long in that environment!).
Anyway, this is going to have to suffice until I can afford to hire a map artist or someone who can illustrate isometric cutaways!