The saying along the top of Rarity's throne are lyrics from Carmina Burana, and they (Ave formosissima, gemma pretiosa) translate into English as "Hail, most beautiful one, precious jewel". Nice work on this picture!
I feel like there should be harpsichord music playing in the background of this scene...
The stained glass mural in the background is especially impressive, but one minor detail you seem to have omitted is Rarity's eye shadow. perhapps that's just the yellow stain you gave the whole canvas, though.
Yes, well casting that spell had many effects... the biggest being that it split the Mane Six.
I mean can you imagine what it was like? Twilight pretty much manipulated Rainbow Dash's sense of loyality and got Pinkie to help as well. Pinkie Pie was killed (though from what I have read I would say more her soul got slingshot into the Astral Plane and her damaged psyche causing her to 'become' the Laughing mare), Rainbow scarred like Two-Face and left seeing one of her friends dead. Rarity got hit with the magical energies causing the disease to set in slowly turning part of her body into crystal. Applejack turned against Twilight more because she supported those she saw as liars since it seemed the sun and moon rose just fine without the sister, though the accident could also play a part. Fluttershy... she didn't go off the deep in until meeting the Everfree Liege and Ponyville was flooded.
Twilight, well she has lost her mentor and her friends. Ponies are calling the one she loves and looks up to a liar, turning against Celestia after all the princess had done for Equestria. ---------
All this coming about because Celestia and Luna just disappear without a trace, leaving ponies confused and without guidance.
So she casts something out of desperation because of the absence of the royal sisters? She didn't know the spell would have such effects, but had faith that it would help anyway. So much faith that she begged her friends to help, and it ruined them. She essentially single handedly threw the land into chaos when the princesses disappeared.
Yes and in a way I feel each of the leaders of the five Houses have become Well-Intentioned Extremist (TV Tropes, look it up).
Antagonists who have an overall goal which the protagonists can appreciate in principle, but whose methods of pursuing said goal (such as mass murder) are problematic; despite any sympathy they may have with their cause, the protagonists have no choice but to stop them.
Odd, I wonder what this is all abou- *clicks on link to source material* *returns an hour later* DAMMIT FOX! STOP INTRODUCING ME TO NEW AWESOMENESS! I HAVE ENOUGH PROJECTS TO MAINTAIN *has to go out and hunt down my muse, who seems to have joined House Everfree* (Seriously though, this is a great work as always from you, normally not a fan of the Grimdark stuff but this AU has certainly captured my attention)