yea. this is a thing. but it actually has nothing to do with the Crystal Empire. it's more about the design elements.

it follows a headcanon that any pony who dies over the gems (presumably amethyst) that grow underneath the Canterlot Castle has their cutie mark (and its associated talents and whatever magicks its former owner possessed) etched into the stone.

so basically, there's these three (technically four, because one of them has two heads) dragons. they take over the old crystal mines beneath Canterlot (the ones that we learned about during the two-part royal wedding thing) and find the mythical Star Swirl the Bearded's cutie mark etched into the crystal in a part close to the former entrance. they all split his power between them and decide to take over Equestria with their newfound power. so after some extra dead-miner-cutie-mark-stealing, they decide to lure ponies in to kill them and take their talents because how else do you become an impossible to defeat final boss?

one of the first ponies they lure in is Rarity. spoiler alert: they spare her. she becomes their servant for a little while, and is given a special pony-dragon form to use in combat and/or when she needs to. the dragons slowly murder Equestria's populous over the course of about 100 years and share all this power with their servant because they trust her, and then eventually, the four alicorn princesses are forced to go down there and put an end to it.

news flash: they (the three dragons + Rarity) have so much power along with their own that they can quickly overwhelm the princesses even without alicorn magic. this is because all of that other magic was allowed to ferment inside their bodies and truly absorb itself into their skills. i know i know, it sounds op but that's okay because they get revived as mindless dragon slave-warriors hours later.

(explanation for trippy logic: i had help from a younger sibling in creating the au)

so now that legit all of Equestria (but Rarity) is dead, the dragons promote their loyal servant to a Princess. they all kind of revive everyone they just killed to be part of their new army...and none of those who were revived remember their past life.

but Rarity has to live with the guilt of knowing that she helped kill her friends. though she's found love in the heart of one of these dragons (because she's dumb enough to think Spike is dead...i'm sorry, i kno, i ship it too...but hearts have gotta break), she still grows hopeless and restless.

what if one of her former friends catches a glimpse of their previous life, of the moment they died? what if they blame their death on her?

——————

So um...if any of you are interested, we can rp this. Or maybe I can drop some more info.

I...just really need to catch up on the series because something's telling me I'm interfering with show canon.