I promise the next one will have actual plot :P until then, enjoy more worldbuilding/lore/headcanons!

Moonstone is cool. She's kind of a Han Solo, puckish rogue type, an adventurer who's clearly lived through dozens of lifetimes and has collected enough experience to have an anecdote ready for every occasion.

She also terrifies Ruby. So much so, the little Corundum has chosen to fly with Lance to the rendezvous point.

It's a fairly short trip, just a couple hours long to traverse some twelve thousand light years to the galactic rim. They could go faster - and the Lions never truly run out of power, pulling a seemingly infinite amount of quintessence from who knows where - but Moonstone suggests caution. Despite Tivan's assurances, they're headed to a sector of the Milky Way that, according to Moonstone, the vast majority of travellers avoid like the plague: the border between Gem and Kree space.

"So, why is the meeting happening all the way out here?" -Pidge asks, some five minutes out.

Moonstone sits beside her on the floor, cross-legged, still tall enough to look down at Pidge. "This is sort of a...buffer zone. The Kree Empire is at war with the Great Diamond Authority - well, they're at war with nearly everybody, really - but it's a rather one-sided affair."

"What do you mean?"

The Gem shrugs. "As powerful, disciplined, and technologically advanced as the Kree are, they really can't compete with the Gem Empire. Can't beat back an enemy that never needs to stop and rest. Or eat. Or wait decades for their warriors to be combat-ready."

"Yikes."

"You said it, sister." -Moonstone agrees. "The Kree still haven't figured out how to stop Gem expansion, so they keep this sector clear of their own colonies as a sort of stop-gap, keeping the Diamonds busy with colonization - which, to be fair, takes them hundreds or even thousands of years to complete for each world."

Pidge raises an eyebrow. "That seems...slow, for your people."

"I'm guessing you haven't seen a finalized Gem colony, then." -she says, cryptically. "In any case, the Kree have been forced to expand elsewhere for the last few thousand years, which is how you get the mess of a galaxy we have today."

"How so?"

Moonstone tilts her head. "What, did you just leave Earth?"

Pidge chuckles awkwardly. "Well, no, but we're more...universe-spanning, I guess. Haven't really been around the Milky Way much, until now."

"Hmm. I see." -she says. "Well, you might not want to stay long, then. This galaxy is on the brink of total war."

"That sounds...less than ideal." -Pidge remarks, sarcastic. "Especially considering Earth is still, like, a point five on the Kardashev scale."

Moonstone looks completely confused, so Pidge coughs and explains. "We can't exactly defend ourselves from alien attacks, I mean. Humanity is still messing around with projectile weaponry and fossil fuels."

"Ah. Well, I wouldn't worry about your home planet too much. Earth has no value to any of the major powers in the galaxy that I know of. It's too remote, too small, and too underdeveloped for the Kree or the Xandarians to consider conquering, and far from the path of the Black Order's so-called Decimation."

Pidge crosses her arms. "Didn't you guys try to conquer the Earth before?"

Moonstone gives her a half-shrug. "Conquering kind of implies violence. Pink Diamond simply claimed Earth as hers, and it's not like your ancestors disagreed - they were barely starting to form their own civilizations. The only Gem-related conflicts on Earth happened due to Rose Quartz's rebellion. No humans were ever actively harmed, to my knowledge."

"Ruby did mention a Quartz…" -Pidge muses.

"I'm surprised she knows about the rebellion at all." -Moonstone admits. "She's an Era 2 Gem, made way after the war ended - she can't be more than a couple centuries old. I thought they couldn't even speak about the shattered Diamond, let alone know about the Crystal Gems."

"And you? How do you know all this?"

Moonstone chuckles. "Well, I'm…old, by organic standards. Somewhere in the late twelve thousands, by my estimation? You kinda stop counting after ten thousand."

"Oh my God, you're older than agriculture." -Pidge shakes her head. "You were alive before the Galra Empire was a thing!"

"I'm older than human agriculture." -she points out, amused. "The Kree had figured industry and machines out by the time your ancestors were beginning to try out sedentarism."

"Wow. That's fascinating." -Pidge says, then shoots her a look. "But it's not quite the explanation I was looking for."

Moonstone raised an eyebrow. "Well, aren't you the curious one." -she says, then gingerly rubs at the gemstone on her thigh. "I suppose there's no point in playing coy: I was part of the first wave of Gem scouts that discovered and landed on Earth, prior to Pink Diamond's attempted colonization."

Pidge blinks. "That's...unbelievable, honestly. What are the odds that you'd end up on a mission with two of a handful of humans currently in space, thousands of years later?"

"Astronomically low, but...you never know, with the Collector. I suspect us meeting was very much intentional on his part." -she shrugs. "If there's anything I've learned in the past few hundred years of service to the man, it's not to question these things. He just...knows, sometimes."

Pidge hums, unsatisfied. Now she kind of wishes they'd spent just a bit more time talking to the eccentric old man. "So, what was it like?" -she asks, after a rather pregnant pause.

"What, Earth?" -she asks, to which Pidge nods. "Beautiful, to be sure. Wild, untamed - I've never seen a world with such an immense variety of life forms before, or since. So densely populated it would've taken every Malachite in the Empire and then some to clear it out."

Right. Anti-organic specialist Gems. As you do.

"Earth was small, for Gem standards at the time, but its sheer resource density made it worth finding, and spending the extra time setting up a direct line to Homeworld. We never imagined it would be Pink Diamond's first colony, much less the site of her death, and of the first and only Gem civil war in history."

"So it's not interesting enough for the Kree or the Xandarians, but it was for Gems?"

Moonstone purses her lips. "Gemkind doesn't exactly have the same criteria for colonization as you fleshy types do. We don't care about atmospheric compositions, flora and fauna, or the presence of water. All we need is a decent enough planetary crust and an abundance of quintessence - the Diamonds provide the rest. Earth would've been a fantastic new colony for the Empire, churned out billions of Gems...at the expense of all life on the planet, of course."

If Green were a car, Pidge would've swerved. As it stands, she only turns, mouth agape, utterly horrified. "What!?"

Moonstone sighs. "Like I said, you haven't seen a completed Gem colony." -she says, then nods to the Lion's viewscreen. "Speaking of which, we're about to overshoot our destination."

Pidge rushes to execute the deceleration sequence, bringing them back into realspace and sub-light speed. A binary star system greets them, the beautiful sight of which fails to bring Pidge out of her shock. Just how close did Pink Diamond and her Gems get to destroying all life on Earth? And how would Gem production have caused such an extinction?

She gets an answer, soon enough. Their destination is a massive, waterlogged terrestrial world, almost thrice the size of Earth. Massive, continent-wide storms reach its upper atmosphere, crackling lightning flaring both towards its watery surface, and reaching at the darkness of space. Even her indestructible cosmic Lion seems apprehensive about approaching.

But it's the planet's largest moon that draws Pidge's attention: a celestial body roughly the size of Mars, but with a hundredth of its mass, owing to the fact that it's been almost completely hollowed out.

Lance sums it up best, over the comms: "What the fuck happened to that planet?"

Green's scans paint a bleak picture. The exposed planetary core seems intact, held together and in place by incredibly powerful magnetic fields. Glowing crystalline rods, thousands of kilometers long, stick into the core and connect it with what little remains of the moon's crust, a patchwork of what must've been continents, held in place by a multitude of gravitational engines, each the size of entire cities. The rods draw geothermal energy from the core, and feed the hundreds of structures dotting the surface. There is no mantle, no asthenosphere, and barely any crust.

Strangely enough, there are no Gems on this world - a tiny reprieve in this sobering moment.

"Now you get it." -Moonstone says, knowingly staring at the Gem colony. "This is how the Empire works. This is how Gems are made."

Prefacing this by saying that I'm bad at math, I calculated the amount of time that Gems take to colonize a planet as "one Grand Canyon a month", which, if you're curious, would mean that Earth would take 8500 years to completely hollow out, as seen in It Could've Been Great. Considering Yellow Diamond outright states that 6000 years is "nothing" to Gems in the SU movie, I feel like that's a perfectly adequate colonization rate. I'd love to hear your take on it, though!